Continuous process for producing electrodes and alkali metal batteries having ultra-high energy densities

ABSTRACT

A process for producing an electrode for an alkali metal battery, comprising: (a) Continuously feeding an electrically conductive porous layer to an anode or cathode material impregnation zone, wherein the conductive porous layer has two opposed porous surfaces and contain interconnected conductive pathways and at least 70% by volume of pores; (b) Impregnating a wet anode or cathode active material mixture into the porous layer from at least one of the two porous surfaces to form an anode or cathode electrode, wherein the wet anode or cathode active material mixture contains an anode or cathode active material and an optional conductive additive mixed with a liquid electrolyte; and (c) Supplying at least a protective film to cover the at least one porous surface to form the electrode.

FIELD OF THE INVENTION

The present invention relates generally to the field of lithiumbatteries, sodium batteries, and potassium batteries, including primary(non-rechargeable) and secondary (rechargeable) alkali metal batteriesand alkali ion batteries.

BACKGROUND OF THE INVENTION

Historically, today's most favorite rechargeable energy storagedevices—lithium-ion batteries—actually evolved from rechargeable“lithium metal batteries” using lithium (Li) metal or Li alloy as theanode and a Li intercalation compound as the cathode. Li metal is anideal anode material due to its light weight (the lightest metal), highelectronegativity (−3.04 V vs. the standard hydrogen electrode), andhigh theoretical capacity (3,860 mAh/g). Based on these outstandingproperties, lithium metal batteries were proposed 40 years ago as anideal system for high energy-density applications. During the mid-1980s,several prototypes of rechargeable Li metal batteries were developed. Anotable example was a battery composed of a Li metal anode and amolybdenum sulfide cathode, developed by MOLI Energy, Inc. (Canada).This and several other batteries from different manufacturers wereabandoned due to a series of safety problems caused by sharply uneven Ligrowth (formation of Li dendrites) as the metal was re-plated duringeach subsequent recharge cycle. As the number of cycles increases, thesedendritic or tree-like Li structures could eventually traverse theseparator to reach the cathode, causing internal short-circuiting.

To overcome these safety issues, several alternative approaches wereproposed in which either the electrolyte or the anode was modified. Oneapproach involved replacing Li metal by graphite (another Li insertionmaterial) as the anode. The operation of such a battery involvesshuttling Li ions between two Li insertion compounds, hence the name“Li-ion battery.” Presumably because of the presence of Li in its ionicrather than metallic state, Li-ion batteries are inherently safer thanLi-metal batteries.

Lithium ion battery is a prime candidate energy storage device forelectric vehicle (EV), renewable energy storage, and smart gridapplications. The past two decades have witnessed a continuousimprovement in Li-ion batteries in terms of energy density, ratecapability, and safety, and somehow the significantly higher energydensity Li metal batteries have been largely overlooked. However, theuse of graphite-based anodes in Li-ion batteries has several significantdrawbacks: low specific capacity (theoretical capacity of 372 mAh/g asopposed to 3,860 mAh/g for Li metal), long Li intercalation time (e.g.low solid-state diffusion coefficients of Li in and out of graphite andinorganic oxide particles) requiring long recharge times (e.g. 7 hoursfor electric vehicle batteries), inability to deliver high pulse power(power density<<1 kW/kg), and necessity to use pre-lithiated cathodes(e.g. lithium cobalt oxide), thereby limiting the choice of availablecathode materials. Further, these commonly used cathodes have arelatively low specific capacity (typically <200 mAh/g). These factorshave contributed to the two major shortcomings of today's Li-ionbatteries—low gravimetric and volumetric energy densities (typically150-220 Wh/kg and 450-600 Wh/L) and low power densities (typically <0.5kW/kg and <1.0 kW/L), all based on the total battery cell weight orvolume.

The emerging EV and renewable energy industries demand the availabilityof rechargeable batteries with a significantly higher gravimetric energydensity (e.g. demanding >>250 Wh/kg and, preferably, >>300 Wh/kg) andhigher power density (shorter recharge times) than what the current Liion battery technology can provide. Furthermore, the microelectronicsindustry is in need of a battery having a significantly largervolumetric energy density (>650 Wh/L, preferably >750 Wh/L) sinceconsumers demand to have smaller-volume and more compact portabledevices (e.g. smart phones and tablets) that store more energy. Theserequirements have triggered considerable research efforts on thedevelopment of electrode materials with a higher specific capacity,excellent rate capability, and good cycle stability for lithium ionbatteries.

Several elements from Group III, IV, and V in the periodic table canform alloys with Li at certain desired voltages. Therefore, variousanode materials based on such elements and some metal oxides have beenproposed for lithium ion batteries. Among these, silicon has beenrecognized as one of the next-generation anode materials for high-energylithium ion batteries since it has a nearly 10 times higher theoreticalgravimetric capacity than graphite 3,590 mAh/g based on Li_(3.75)Si vs.372 mAh/g for LiC₆) and ˜3 times larger volumetric capacities. However,the dramatic volume changes (up to 380%) of Si during lithium ionalloying and de-alloying (cell charge and discharge) often led to severeand rapid battery performance deterioration. The performance fade ismainly due to the volume change-induced pulverization of Si and theinability of the binder/conductive additive to maintain the electricalcontact between the pulverized Si particles and the current collector.In addition, the intrinsic low electric conductivity of silicon isanother challenge that needs to be addressed.

Although several high-capacity anode active materials have been found(e.g., Si), there has been no corresponding high-capacity cathodematerial available. Current cathode active materials commonly used inLi-ion batteries have the following serious drawbacks:

-   -   (1) The practical capacity achievable with current cathode        materials (e.g. lithium iron phosphate and lithium transition        metal oxides) has been limited to the range of 150-250 mAh/g        and, in most cases, less than 200 mAh/g.    -   (2) The insertion and extraction of lithium in and out of these        commonly used cathodes rely upon extremely slow solid-state        diffusion of Li in solid particles having very low diffusion        coefficients (typically 10⁻⁸ to 10⁻¹⁴ cm²/s), leading to a very        low power density (another long-standing problem of today's        lithium-ion batteries).    -   (3) The current cathode materials are electrically and thermally        insulating, not capable of effectively and efficiently        transporting electrons and heat. The low electrical conductivity        means high internal resistance and the necessity to add a large        amount of conductive additives, effectively reducing the        proportion of electrochemically active material in the cathode        that already has a low capacity. The low thermal conductivity        also implies a higher tendency to undergo thermal runaway, a        major safety issue in lithium battery industry.

As a totally distinct class of energy storage device, sodium batterieshave been considered an attractive alternative to lithium batteriessince sodium is abundant and the production of sodium is significantlymore environmentally benign compared to the production of lithium. Inaddition, the high cost of lithium is a major issue and Na batteriespotentially can be of significantly lower cost.

There are at least two types of batteries that operate on bouncingsodium ions (Na⁺) back and forth between an anode and a cathode: thesodium metal battery having Na metal or alloy as the anode activematerial and the sodium-ion battery having a Na intercalation compoundas the anode active material. Sodium ion batteries using a hardcarbon-based anode active material (a Na intercalation compound) and asodium transition metal phosphate as a cathode have been described byseveral research groups; e.g. J. Barker, et al. “Sodium Ion Batteries,”U.S. Pat. No. 7,759,008 (Jul. 20, 2010).

However, these sodium-based devices exhibit even lower specific energiesand rate capabilities than Li-ion batteries. The anode active materialsfor Na intercalation and the cathode active materials for Naintercalation have lower Na storage capacities as compared with their Listorage capacities. For instance, hard carbon particles are capable ofstoring Li ions up to 300-360 mAh/g, but the same materials can store Naions up to 150-250 mAh/g and less than 100 mAh/g for K ion storage.

Instead of hard carbon or other carbonaceous intercalation compound,sodium metal may be used as the anode active material in a sodium metalcell. However, the use of metallic sodium as the anode active materialis normally considered undesirable and dangerous due to the dendriteformation, interface aging, and electrolyte incompatibility problems.

Low-capacity anode or cathode active materials are not the only problemthat the alkali metal-ion battery industry faces. There are seriousdesign and manufacturing issues that the lithium-ion battery industrydoes not seem to be aware of, or has largely ignored. For instance,despite the high gravimetric capacities at the electrode level (based onthe anode or cathode active material weight alone) as frequently claimedin open literature and patent documents, these electrodes unfortunatelyfail to provide batteries with high capacities at the battery cell orpack level (based on the total battery cell weight or pack weight). Thisis due to the notion that, in these reports, the actual active materialmass loadings of the electrodes are too low. In most cases, the activematerial mass loadings of the anode (areal density) is significantlylower than 15 mg/cm² and mostly <8 mg/cm² (areal density=the amount ofactive materials per electrode cross-sectional area along the electrodethickness direction). The cathode active material amount is typically1.5-2.5 times higher than the anode active material. As a result, theweight proportion of the anode active material (e.g. graphite or carbon)in a lithium-ion battery is typically from 12% to 17%, and that of thecathode active material (e.g. LiMn₂O₄) from 17% to 35% (mostly <30%).The weight fraction of the cathode and anode active materials combinedis typically from 30% to 45% of the cell weight

The low active material mass loading is primarily due to the inabilityto obtain thicker electrodes (thicker than 100-200 μm) using theconventional slurry coating procedure. This is not a trivial task as onemight think, and in reality the electrode thickness is not a designparameter that can be arbitrarily and freely varied for the purpose ofoptimizing the cell performance. Contrarily, thicker samples tend tobecome extremely brittle or of poor structural integrity and would alsorequire the use of large amounts of binder resin. The low arealdensities and low volume densities (related to thin electrodes and poorpacking density) result in a relatively low volumetric capacity and lowvolumetric energy density of the battery cells. Sodium-ion batteries andpotassium-ion batteries have similar problems.

With the growing demand for more compact and portable energy storagesystems, there is keen interest to increase the utilization of thevolume of the batteries. Novel electrode materials and designs thatenable high volumetric capacities and high mass loadings are essentialto achieving improved cell volumetric capacities and energy densitiesfor alkali metal batteries.

Therefore, there is clear and urgent need for alkali metal batteriesthat have high active material mass loading (high areal density), activematerials with high apparent density (high tap density), high electrodethickness without significantly decreasing the electron and iontransport rates (e.g. without a high electron transport resistance orlong lithium or sodium ion diffusion path), high volumetric capacity,and high volumetric energy density.

SUMMARY OF THE INVENTION

The present invention provides a process for producing an alkali metalbattery having a high active material mass loading, exceptionally lowoverhead weight and volume (relative to the active material mass andvolume), high volumetric capacity, and unprecedentedly high volumetricenergy density and power density. This alkali metal battery can be aprimary battery (non-rechargeable) or a secondary battery(rechargeable), including a rechargeable alkali metal battery (having alithium, sodium, or potassium metal anode) and an alkali metal-ionbattery (e.g. having a first lithium or sodium intercalation compound asan anode active material and a second lithium or sodium intercalation orabsorbing compound, having a much higher electrochemical potential thanthe first one, as a cathode active material). The electrochemicalpotential of the cathode active material is higher than that of theanode active material by at least 1.0 volt, preferably at least 1.5volts, further preferably at least 2.0 volts, more preferably at least3.0 volts, even more preferably at least 3.5 volts, and most preferablyat least 4.0 volts.

In one embodiment, the invention provides a process for producing analkali metal-ion battery wherein the alkali metal is selected from Li,Na, K, Cs, or a combination thereof; the process comprising:

-   -   (A) Continuously feeding an electrically conductive porous layer        to a cathode material impregnation zone, wherein the conductive        porous layer has two opposed porous surfaces and contain        interconnected conductive pathways and at least 70% by volume of        pores (preferably >80%, more preferably >90%, and most        preferably >95%);    -   (B) Impregnating a wet cathode active material mixture into the        electrically conductive porous layer from at least one of the        two porous surfaces to form a cathode electrode, wherein the wet        cathode active material mixture contains a cathode active        material and an optional conductive additive mixed with a first        liquid electrolyte (although a binder resin can be optionally        added, but this is undesirable);    -   (C) Continuously feeding an electrically conductive porous layer        to an anode material impregnation zone, wherein the conductive        porous layer has two opposed porous surfaces and contain        interconnected conductive pathways and at least 70%        (preferably >80%) by volume of pores;    -   (D) Impregnating a wet anode active material mixture into the        electrically conductive porous layer from at least one of the        two porous surfaces to form an anode electrode, wherein the wet        anode active material mixture contains an anode active material        and an optional conductive additive mixed with a second liquid        electrolyte; and    -   (E) Stacking the anode electrode, a porous separator, and the        cathode electrode to form the alkali metal battery, wherein the        anode electrode and/or the cathode electrode has a thickness no        less than 100 μm; the anode active material has a material mass        loading no less than 20 mg/cm² in the anode electrode; and/or        the cathode active material has a material mass loading no less        than 15 mg/cm² for an organic or polymer material or no less        than 30 mg/cm² for an inorganic and non-polymer material in the        cathode electrode.

In some embodiments, step (A) and step (B) include delivering,continuously or intermittently on demand, the wet cathode activematerial mixture to the at least one porous surface through spraying,printing, coating, casting, conveyor film delivery, and/or rollersurface delivery. In some embodiments, step (C) and step (D) includedelivering, continuously or intermittently on demand, the wet anodeactive material mixture to the at least one porous surface throughspraying, printing, coating, casting, conveyor film delivery, and/orroller surface delivery.

The cathode electrode thickness or the anode electrode thickness ispreferably >200 μm, further preferably >300 μm, more preferably >400 μm;further more preferably >500 μm, still more preferably >600 μm, oreven >1,000 μm; no theoretical limitation on the thickness of thepresently invented electrode. It may be noted that, in step (E), aplurality of cathode electrode layers (e.g. those prepared in steps (A)and (B)) can be combined and consolidated into one single cathodeelectrode to make a significantly thicker cathode electrode, if sodesired. Similarly, if necessary, several anode electrode layers (e.g.as those prepared by steps (C) and (D)) can be combined and consolidatedinto one single anode electrode layer to make a significantly thickeranode electrode.

The invention also provides a process for producing an alkali metal-ionbattery wherein the anode active material is alkali metal or alloy(metal or alloy of Li, Na, K, Cs, or a combination thereof). In apreferred embodiment, the process comprises:

-   -   (A) Continuously feeding an electrically conductive porous layer        to a cathode material impregnation zone, wherein the conductive        porous layer has two opposed porous surfaces and contain        interconnected conductive pathways and at least 70%        (preferably >80% and more preferably >90%) by volume of pores;    -   (B) Impregnating a wet cathode active material mixture into the        electrically conductive porous layer from at least one of the        two porous surfaces to form a cathode electrode, wherein the wet        cathode active material mixture contains a cathode active        material and an optional conductive additive mixed with a first        liquid electrolyte;    -   (C) Continuously introducing an anode electrode having an anode        current collector that has two opposed primary surfaces wherein        at least one of the two primary surfaces is deposited with a        layer of alkali metal or alkali metal alloy having at least 50%        by weight of an alkali metal element in said alloy        (preferably >70%, further preferably >80%, and most        preferably >90% by weight of an alkali metal element, such as        Li, Na, and/or K); and    -   (D) Stacking the anode electrode, a porous separator, and the        cathode electrode to form the alkali metal battery, wherein the        cathode electrode has a thickness no less than 100 μm        (preferably >200 μm, further preferably >300 μm, more        preferably >400 μm; further more preferably >500 μm, 600 μm, or        even >1,000 μm); the cathode active material has a material mass        loading no less than 15 mg/cm² for an organic or polymer        material or no less than 30 mg/cm² for an inorganic and        non-polymer material in the cathode electrode.        In some embodiments, step (A) and step (B) include delivering,        continuously or intermittently on demand, the wet cathode active        material mixture to the at least one porous surface through        spraying, printing, coating, casting, conveyor film delivery,        and/or roller surface delivery. The anode electrode of this        alkali metal-ion battery is basically composed of a solid        current collector (e.g. Cu foil) coated with a thin film of Li,        Na, Li metal alloy, or Na metal alloy, etc.

In some embodiments wherein the alkali metal battery is a lithium-ionbattery, the anode active material may be selected from the groupconsisting of: (a) Particles of natural graphite, artificial graphite,meso-carbon microbeads (MCMB), and carbon; (b) Silicon (Si), germanium(Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn),aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti),iron (Fe), and cadmium (Cd); (c) Alloys or intermetallic compounds ofSi, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements, wherein saidalloys or compounds are stoichiometric or non-stoichiometric; (d)Oxides, carbides, nitrides, sulfides, phosphides, selenides, andtellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti, Mn, or Cd,and their mixtures or composites; (e) Pre-lithiated versions thereof;and (f) Pre-lithiated graphene sheets; and combinations thereof.

There is no restriction on the types of anode active materials orcathode active materials that can be used in practicing the instantinvention. However, preferably, the anode active material absorbslithium ions at an electrochemical potential of less than 1.0 volt(preferably less than 0.7 volts) above the Li/Li⁺ (i.e. relative toLi→Li⁺+e⁻ as the standard potential) when the battery is charged. Theanode active material for Na-ion or K-ion battery can be similarlychosen.

In a preferred embodiment, the anode active material is a pre-sodiatedor pre-potassiated version of graphene sheets selected from pristinegraphene, graphene oxide, reduced graphene oxide, graphene fluoride,graphene chloride, graphene bromide, graphene iodide, hydrogenatedgraphene, nitrogenated graphene, chemically functionalized graphene, ora combination thereof. The starting graphitic material for producing anyone of the above graphene materials may be selected from naturalgraphite, artificial graphite, meso-phase carbon, meso-phase pitch,meso-carbon micro-bead, soft carbon, hard carbon, coke, carbon fiber,carbon nano-fiber, carbon nano-tube, or a combination thereof. Graphenematerials are also a good conductive additive for both the anode andcathode active materials of an alkali metal battery.

In some embodiments, the alkali metal battery is a sodium-ion batteryand the anode active material contains an alkali intercalation compoundselected from petroleum coke, carbon black, amorphous carbon, activatedcarbon, hard carbon, soft carbon, templated carbon, hollow carbonnanowires, hollow carbon sphere, titanates, NaTi₂(PO₄)₃, Na₂Ti₃O₇,Na₂C₈H₄O₄, Na₂TP, Na_(x)TiO₂ (x=0.2 to 1.0), Na₂C₈H₄O₄, carboxylatebased materials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄, C₁₀H₂Na₄O₈,C₁₄H₄O₆, C₁₄H₄Na₄O₈, or a combination thereof.

In some embodiments, the alkali metal battery is a sodium-ion battery orpotassium-ion battery and the anode active material contains an alkaliintercalation compound selected from the following groups of materials:(a) Sodium- or potassium-doped silicon (Si), germanium (Ge), tin (Sn),lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al),titanium (Ti), cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd),and mixtures thereof; (b) Sodium- or potassium-containing alloys orintermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni,Mn, Cd, and their mixtures; (c) Sodium- or potassium-containing oxides,carbides, nitrides, sulfides, phosphides, selenides, tellurides, orantimonides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd,and mixtures or composites thereof; (d) Sodium or potassium salts; and(e) Graphene sheets pre-loaded with sodium ions or potassium ions.

In some embodiments, the cathode active material contains a lithiumintercalation compound or lithium absorbing compound selected from thegroup consisting of lithium cobalt oxide, doped lithium cobalt oxide,lithium nickel oxide, doped lithium nickel oxide, lithium manganeseoxide, doped lithium manganese oxide, lithium vanadium oxide, dopedlithium vanadium oxide, lithium mixed-metal oxides, lithium ironphosphate, lithium vanadium phosphate, lithium manganese phosphate,lithium mixed-metal phosphates, metal sulfides, lithium polysulfide,sulfur, and combinations thereof.

In some embodiments, the cathode active material contains a sodiumintercalation compound or a potassium intercalation compound selectedfrom NaFePO₄, Na_((1-x))K_(x)PO₄, KFePO₄, Na_(0.7)FePO₄,Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃, Na₂FePO₄F, NaFeF₃,NaVPO₄F, KVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃,NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂,Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂,λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈,NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, KCrO₂, Na₃Ti₂(PO₄)₃,NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F,Se_(z)S_(y) (y/z=0.01 to 100), Se, sodium polysulfide, sulfur,Alluaudites, or a combination thereof, wherein x is from 0.1 to 1.0.

There is no theoretical limitation on the thickness of electricallyconductive porous layers. They may each have a thickness from 50 μm to2,000 μm (or thicker), preferably from 100 μm to 800 μm, furtherpreferably from 200 μm to 600 μm. These desired thickness rangesfacilitate the infiltration of the wet anode active mixture (liquidelectrolyte, anode active material, and optional conductive additive) orwet cathode active mixture (liquid electrolyte, cathode active material,and optional conductive additive) during the consolidation step.

The electrically conductive porous layers may be selected from metalfoam, metal web or screen, perforated metal sheet-based 3-D structure,metal fiber mat, metal nanowire mat, conductive polymer nano-fiber mat,conductive polymer foam, conductive polymer-coated fiber foam, carbonfoam, graphite foam, carbon aerogel, carbon xerox gel, graphene foam,graphene oxide foam, reduced graphene oxide foam, carbon fiber foam,graphite fiber foam, exfoliated graphite foam, or a combination thereof.These multiple electrically conductive porous layers, when consolidated(compressed) together, make a good current collector at the anode or thecathode. No separate or additional current collector is required orneeded.

The pore volume (e.g. >80%) of the electrically conductive porous layersis a critically important requirement to ensure a large proportion ofactive materials accommodated in the current collector. Based on thiscriterion, conventional paper or textiles made of natural and/orsynthetic fibers do not meet this requirement since they do not have asufficient amount of properly sized pores (e.g. the anode activematerials or cathode active materials could not infiltrate into thepores of these paper or textile structures).

The pore sizes in the electrically conductive porous layers arepreferably in the range from 10 nm to 100 μm, more preferably from 100nm to 50 μm, further preferably from 500 nm to 20 μm, and even morepreferably from 1 μm to 10 μm, and most preferably from 1 μm to 5 μm.These pore size ranges are designed to accommodate anode activematerials (such as graphite micron particles or Si nano particles) andcathode active materials (such as lithium cobalt oxide or lithium ironphosphate), having a primary or secondary particle size typically from10 nm to 20 μm in diameter, and most typically from 50 nm to 10 μm,further typically from 100 nm to 5 μm, and most typically from 200 nm to3 μm.

More significantly, however, since all active material particles in apore (e.g. with pore size of 5 μm) are, on average, within a distance of2.5 μm from a pore wall (electron-conducting pathway) in theelectrically conductive porous layers structure, electrons can bereadily collected from the anode active material particle and alkalimetal ions (e.g. lithium ions) do not have to undergo a long-distancesolid-state diffusion. This is in contrast to the notion that someelectrons in the conventional thick electrode of prior art lithium-ionbattery (e.g. wherein Si particle layer>100 μm in thickness is coatedonto a surface of a solid Cu foil current collector 10 μm thick) musttravel at least 50 μm through conductive additive particles to getcollected by a current collector. These conductive additive particlesare typically not in good electronic contact with one another (e.g.interrupted by a non-conductive binder resin), leading to a largeinternal resistance and reduced ability to deliver a higher power.

In general, the first liquid electrolyte and the second liquidelectrolyte are identical in a battery, but they can be different incomposition. The liquid electrolytes can be an aqueous liquid, organicliquid, ionic liquid (ionic salt having a melting temperature lower than100° C., preferably lower than room temperature, 25° C.), or a mixtureof an ionic liquid and an organic liquid at a ratio from 1/100 to 100/1.The organic liquid is desirable, but the ionic liquid is preferred. Agel electrolyte can also be used provided the electrolyte has somemobility to enable infiltration of wet anode or cathode materials.

In a preferred embodiment, the consolidated anode and/or cathodeelectrodes have a thickness no less than 200 μm; the electricallyconductive porous layers have at least 85% by volume of pores; the anodeactive material has a mass loading no less than 25 mg/cm² and/oroccupies at least 25% by weight or by volume of the entire battery cell;the cathode active material has a mass loading no less than 20 mg/cm²for an organic or polymer material or no less than 40 mg/cm² for aninorganic and non-polymer material in the cathode and/or occupies atleast 40% by weight or by volume of the entire battery cell.

In another preferred embodiment, the consolidated anode and/or cathodeelectrodes have a thickness no less than 300 μm; the electricallyconductive porous layers have at least 90% by volume of pores; the anodeactive material has a mass loading no less than 30 mg/cm² and/oroccupies at least 30% by weight or by volume of the entire battery cell,and/or the cathode active material has a mass loading no less than 25mg/cm² for an organic or polymer material or no less than 50 mg/cm² foran inorganic and non-polymer material in said cathode and/or occupies atleast 50% by weight or by volume of the entire battery cell.

More preferably, the consolidated anode and/or cathode electrodes have athickness no less than 400 μm; the electrically conductive porous layershave at least 95% by volume of pores, and/or said anode active materialhas a mass loading no less than 35 mg/cm² and/or occupies at least 35%by weight or by volume of the entire battery cell, and/or the cathodeactive material has a mass loading no less than 30 mg/cm² for an organicor polymer material or no less than 55 mg/cm² for an inorganic andnon-polymer material in the cathode and/or occupies at least 55% byweight or by volume of the entire battery cell.

The aforementioned requirements on electrode thickness, porosity levels,the anode active material areal mass loading or mass fraction relativeto the entire battery cell, or the cathode active material areal massloading or mass fraction relative to the entire battery cell have notbeen possible with conventional lithium batteries using the conventionalprocess of slurry coating and drying.

In some embodiments, the anode active material is a pre-lithiatedversion of graphene sheets selected from pristine graphene, grapheneoxide, reduced graphene oxide, graphene fluoride, graphene chloride,graphene bromide, graphene iodide, hydrogenated graphene, nitrogenatedgraphene, boron-doped graphene, nitrogen-doped graphene, chemicallyfunctionalized graphene, a physically or chemically activated or etchedversion thereof, or a combination thereof. Surprisingly, withoutpre-lithiation, the resulting lithium battery cell does not exhibit asatisfactory cycle life (i.e. capacity decays rapidly).

Preferably, the volume ratio of the anode active material-to-liquidelectrolyte in the wet anode active material mixture is from 1/5 to 20/1(preferably from 1/3 to 5/1) and/or the volume ratio of cathode activematerial-to-the liquid electrolyte in the wet cathode active materialmixture is from 1/5 to 20/1 (preferably from 1/3 to 5/1).

In some embodiments, the cathode active material in this alkali metalbattery contains an alkali metal intercalation compound or alkalimetal-absorbing compound selected from an inorganic material, an organicor polymeric material, a metal oxide/phosphate/sulfide, or a combinationthereof. For example, the metal oxide/phosphate/sulfide may be selectedfrom a lithium cobalt oxide, lithium nickel oxide, lithium manganeseoxide, lithium vanadium oxide, lithium-mixed metal oxide, lithium ironphosphate, lithium manganese phosphate, lithium vanadium phosphate,lithium mixed metal phosphate, transition metal sulfide, or acombination thereof. The inorganic material is selected from sulfur,sulfur compound, lithium polysulfide, transition metal dichalcogenide, atransition metal trichalcogenide, or a combination thereof. Inparticular, the inorganic material is selected from TiS₂, TaS₂, MoS₂,NbSe₃, MnO₂, CoO₂, an iron oxide, a vanadium oxide, or a combinationthereof. These will be further discussed later.

In some embodiments, the cathode active material contains an alkalimetal intercalation compound selected from a metal carbide, metalnitride, metal boride, metal dichalcogenide, or a combination thereof.In some embodiments, the cathode active material contains an alkalimetal intercalation compound selected from an oxide, dichalcogenide,trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium,molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium,cobalt, manganese, iron, or nickel in a nanowire, nano-disc,nano-ribbon, or nano platelet form. Preferably, the cathode activematerial contains a lithium intercalation compound selected from nanodiscs, nano platelets, nano-coating, or nano sheets of an inorganicmaterial selected from: (a) bismuth selenide or bismuth telluride, (b)transition metal dichalcogenide or trichalcogenide, (c) sulfide,selenide, or telluride of niobium, zirconium, molybdenum, hafnium,tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or atransition metal; (d) boron nitride, or (e) a combination thereof;wherein these discs, platelets, or sheets have a thickness less than 100nm.

In some embodiments, the cathode active material in this alkali metalbattery is an organic material or polymeric material selected fromPoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).

In a preferred embodiment, the cathode active material is an organicmaterial containing a phthalocyanine compound selected from copperphthalocyanine, zinc phthalocyanine, tin phthalocyanine, ironphthalocyanine, lead phthalocyanine, nickel phthalocyanine, vanadylphthalocyanine, fluorochromium phthalocyanine, magnesium phthalocyanine,manganous phthalocyanine, dilithium phthalocyanine, aluminumphthalocyanine chloride, cadmium phthalocyanine, chlorogalliumphthalocyanine, cobalt phthalocyanine, silver phthalocyanine, ametal-free phthalocyanine, a chemical derivative thereof, or acombination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) schematic of a prior art lithium-ion battery cell (as anexample of an alkali metal battery) composed of an anode currentcollector, an anode electrode (e g thin Si coating layer), a porousseparator, a cathode electrode (e.g. sulfur layer), and a cathodecurrent collector;

FIG. 1(B) schematic of a prior art lithium-ion battery, wherein theelectrode layer is composed of discrete particles of an active material(e.g. graphite or tin oxide particles in the anode layer or LiCoO₂ inthe cathode layer).

FIG. 1(C) Four examples that schematically illustrate the presentlyinvented process for producing an electrode (anode or cathode) of analkali metal battery.

FIG. 1(D) Another example to schematically illustrate the presentlyinvented process to produce an electrode (anode or cathode).

FIG. 1(E) Schematic of a presently invented process for continuouslyproducing an alkali metal-ion battery by combining and laminating ananode electrode, separator, and cathode electrode (illustrated inSchematic F), and that for continuously producing an alkali metalbattery laminate in an automated manner (Schematic G); the latterbattery comprising an anode current collector containing a layer of analkali metal (e.g. lithium metal) or alkali metal alloy (e.g. lithiummetal alloy) deposited thereon, a porous separator, and a cathodeelectrode.

FIG. 2 An electron microscopic image of graphene sheets.

FIG. 3(A) Examples of conductive porous layers: metal grid/mesh andcarbon nano-fiber mat.

FIG. 3(B) Examples of conductive porous layers: graphene foam and carbonfoam.

FIG. 3(C) Examples of conductive porous layers: graphite foam and Nifoam.

FIG. 3(D) Examples of conductive porous layers: Cu foam and stainlesssteel foam.

FIG. 4(A) Schematic of a commonly used process for producing exfoliatedgraphite, expanded graphite flakes (thickness>100 nm), and graphenesheets (thickness<100 nm, more typically <10 nm, and can be as thin as0.34 nm).

FIG. 4(B) Schematic drawing to illustrate the processes for producingexfoliated graphite, expanded graphite flakes, and graphene sheets.

FIG. 5 Ragone plots (gravimetric and volumetric power density vs. energydensity) of lithium-ion battery cells containing graphite particles asthe anode active material and carbon-coated LFP particles as the cathodeactive materials. Two of the 4 data curves are for the cells preparedaccording to an embodiment of instant invention and the other two by theconventional slurry coating of electrodes (roll-coating).

FIG. 6 Ragone plots (both gravimetric and volumetric power density vs.gravimetric and volumetric energy density) of two cells, both containinggraphene-embraced Si nano particles as the anode active material andLiCoO₂ nano particles as the cathode active material. The experimentaldata were obtained from the Li-ion battery cells that were prepared bythe presently invented method and those by the conventional slurrycoating of electrodes.

FIG. 7 Ragone plots of lithium metal batteries containing a lithium foilas the anode active material, dilithium rhodizonate (Li₂C₆O₆) as thecathode active material, and lithium salt (LiPF₆)-PC/DEC as organicliquid electrolyte. The data are for both lithium metal cells preparedby the presently invented method and those by the conventional slurrycoating of electrodes.

FIG. 8 The cell-level gravimetric (Wh/kg) and volumetric energydensities (Wh/L) of lithium metal cells plotted over the achievablecathode thickness range of the MnO₂/RGO cathode prepared via theconventional method without delamination and cracking and those by thepresently invented method. In this figure, the data points are labelledas the gravimetric (♦) and volumetric (▴) energy density of theconventional Li—MnO₂/RGO batteries and the gravimetric (▪) andvolumetric (x) energy density of the presently invented ones.

FIG. 9 The cell-level gravimetric and volumetric energy densities of thegraphite/NMC cells prepared by the presently invented method and thoseby the conventional roll-coating method.

FIG. 10 Ragone plots (gravimetric and volumetric power density vs.energy density) of Na-ion battery cells containing hard carbon particlesas the anode active material and carbon-coated Na₃V₂(PO₄)₂F₃ particlesas the cathode active materials. Two of the 4 data curves are for thecells prepared according to an embodiment of instant invention and theother two by the conventional slurry coating of electrodes(roll-coating).

FIG. 11 Ragone plots (both gravimetric and volumetric power density vs.gravimetric and volumetric energy density) of two cells, both containinggraphene-embraced Sn nano particles as the anode active material andNaFePO₄ nano particles as the cathode active material. The data are forboth sodium-ion cells prepared by the presently invented method andthose by the conventional slurry coating of electrodes.

FIG. 12 Ragone plots of sodium metal batteries containing agraphene-supported sodium foil as the anode active material, disodiumrhodizonate (Na₂C₆O₆) as the cathode active material, and sodium salt(NaPF₆)-PC/DEC as organic liquid electrolyte. The data are for bothsodium metal cells prepared by the presently invented method and thoseby the conventional slurry coating of electrodes.

FIG. 13 Ragone plot of a series of K-ion cells prepared by theconventional slurry coating process and the Ragone plot of correspondingK-ion cells prepared by the presently invented process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be understood more readily by reference to thefollowing detailed description of the invention taken in connection withthe accompanying drawing figures, which form a part of this disclosure.It is to be understood that this invention is not limited to thespecific devices, methods, conditions or parameters described and/orshown herein, and that the terminology used herein is for the purpose ofdescribing particular embodiments by way of example only and is notintended to be limiting of the claimed invention.

This invention is directed at a process for producing an alkali metalbattery exhibiting an exceptionally high volumetric energy density thathas never been previously achieved for the same type of alkali metalbattery. This alkali metal battery can be a primary battery, but ispreferably a secondary battery selected from a lithium-ion battery or alithium metal secondary battery (e.g. using lithium metal as an anodeactive material), a sodium-ion battery, a sodium metal battery, apotassium-ion battery, or a potassium metal battery. The battery isbased on an aqueous electrolyte, a non-aqueous or organic electrolyte, agel electrolyte, an ionic liquid electrolyte, or a mixture of organicand ionic liquid. The final shape of an alkali metal battery can becylindrical, square, button-like, etc. The present invention is notlimited to any battery shape or configuration.

For convenience, we will use selected materials, such as lithium ironphosphate (LFP), vanadium oxide (V_(x)O_(y)), lithium nickel manganesecobalt oxide (NMC), dilithium rhodizonate (Li₂C₆O₆), and copperphthalocyanine (CuPc) as illustrative examples of the cathode activematerial, and graphite, SnO, Co₃O₄, and Si particles as examples of theanode active material. For sodium batteries, we will use selectedmaterials, such as NaFePO₄ and λ-MnO₂ particles, as illustrativeexamples of the cathode active material, and hard carbon and NaTi₂(PO₄)₃particles as examples of the anode active material of a Na-ion cell.Similar approaches are applicable to K-ion batteries. Nickel foam,graphite foam, graphene foam, and stainless steel fiber webs are used asexamples of conductive porous layers as intended current collectors.These should not be construed as limiting the scope of the invention.

As illustrated in FIGS. 1(A) and 1(B), a lithium-ion battery cell istypically composed of an anode current collector (e.g. Cu foil), ananode electrode (anode active material layer), a porous separator and/oran electrolyte component, a cathode electrode (cathode active materiallayer), and a cathode current collector (e.g. Al foil). In a morecommonly used cell configuration (FIG. 1(B)), the anode layer iscomposed of particles of an anode active material (e.g. graphite or Si),a conductive additive (e.g. carbon black particles), and a resin binder(e.g. SBR or PVDF). The cathode layer is composed of particles of acathode active material (e.g. LFP particles), a conductive additive(e.g. carbon black particles), and a resin binder (e.g. PVDF). Both theanode and the cathode layers are typically up to 100-200 μm thick togive rise to a presumably sufficient amount of current per unitelectrode area. This thickness range is considered an industry-acceptedconstraint under which a battery designer normally works under. Thisthickness constraint is due to several reasons: (a) the existing batteryelectrode coating machines are not equipped to coat excessively thin orexcessively thick electrode layers; (b) a thinner layer is preferredbased on the consideration of reduced lithium ion diffusion pathlengths; but, too thin a layer (e.g. <100 μm) does not contain asufficient amount of an active lithium storage material (hence,insufficient current output); (c) thicker electrodes are prone todelaminate or crack upon drying or handling after roll-coating; and (d)all non-active material layers in a battery cell (e.g. currentcollectors and separator) must be kept to a minimum in order to obtain aminimum overhead weight and a maximum lithium storage capability and,hence, a maximized energy density (Wk/kg or Wh/L of cell).

In a less commonly used cell configuration, as illustrated in FIG. 1(A),either the anode active material (e.g. Si) or the cathode activematerial (e.g. lithium transition metal oxide) is deposited in a thinfilm form directly onto a current collector, such as a sheet of copperfoil or Al foil. However, such a thin film structure with an extremelysmall thickness-direction dimension (typically much smaller than 500 nm,often necessarily thinner than 100 nm) implies that only a small amountof active material can be incorporated in an electrode (given the sameelectrode or current collector surface area), providing a low totallithium storage capacity and low lithium storage capacity per unitelectrode surface area. Such a thin film must have a thickness less than100 nm to be more resistant to cycling-induced cracking (for the anode)or to facilitate a full utilization of the cathode active material. Sucha constraint further diminishes the total lithium storage capacity andthe lithium storage capacity per unit electrode surface area. Such athin-film battery has very limited scope of application.

On the anode side, a Si layer thicker than 100 nm has been found toexhibit poor cracking resistance during battery charge/discharge cycles.It takes but a few cycles to get fragmented. On the cathode side, asputtered layer of lithium metal oxide thicker than 100 nm does notallow lithium ions to fully penetrate and reach full body of the cathodelayer, resulting in a poor cathode active material utilization rate. Adesirable electrode thickness is at least 100 μm, with individual activematerial coating or particle having a dimension desirably less than 100nm. Thus, these thin-film electrodes (with a thickness<100 nm) directlydeposited on a current collector fall short of the required thickness bythree (3) orders of magnitude. As a further problem, all of the cathodeactive materials are not conductive to both electrons and lithium ions.A large layer thickness implies an excessively high internal resistanceand a poor active material utilization rate.

In other words, there are several conflicting factors that must beconsidered concurrently when it comes to the design and selection of acathode or anode active material in terms of material type, size,electrode layer thickness, and active material mass loading. Thus far,there has been no effective solution offered by any prior art teachingto these often conflicting problems. We have solved these challengingissues, which have troubled battery designers and electrochemists alikefor more than 30 years, by developing a new process of producing lithiumbatteries as herein disclosed.

The prior art lithium battery cell is typically made by a process thatincludes the following steps: (a) The first step includes mixingparticles of the anode active material (e.g. Si nano particles ormeso-carbon micro-beads, MCMBs), a conductive filler (e.g. graphiteflakes), a resin binder (e.g. PVDF) in a solvent (e.g. NMP) to form ananode slurry. On a separate basis, particles of the cathode activematerial (e.g. LFP particles), a conductive filler (e.g. acetyleneblack), a resin binder (e.g. PVDF) are mixed and dispersed in a solvent(e.g. NMP) to form a cathode slurry. (b) The second step includescoating the anode slurry onto one or both primary surfaces of an anodecurrent collector (e.g. Cu foil), drying the coated layer by vaporizingthe solvent (e.g. NMP) to form a dried anode electrode coated on Cufoil. Similarly, the cathode slurry is coated and dried to form a driedcathode electrode coated on Al foil. Slurry coating is normally done ina roll-to-roll manner in a real manufacturing situation; (c) The thirdstep includes laminating an anode/Cu foil sheet, a porous separatorlayer, and a cathode/Al foil sheet together to form a 3-layer or 5-layerassembly, which is cut and slit into desired sizes and stacked to form arectangular structure (as an example of shape) or rolled into acylindrical cell structure. (d) The rectangular or cylindrical laminatedstructure is then encased in an aluminum-plastic laminated envelope orsteel casing. (e) A liquid electrolyte is then injected into thelaminated structure to make a lithium battery cell.

There are several serious problems associated with the conventionalprocess and the resulting lithium-ion battery cell or sodium-ion cell:

-   -   1) It is very difficult to produce an electrode layer (anode        layer or cathode layer) that is thicker than 200 μm (100 μm on        each side of a solid current collector, such as Al foil). There        are several reasons why this is the case. An electrode of        100-200 μm in thickness typically requires a heating zone of        30-50 meters long in a slurry coating facility, which is too        time consuming, too energy intensive, and not cost-effective.        For some electrode active materials, such as metal oxide        particles, it has not been possible to produce an electrode of        good structural integrity that is thicker than 100 μm in a real        manufacturing environment on a continuous basis. The resulting        electrodes are very fragile and brittle. Thicker electrodes have        a high tendency to delaminate and crack.    -   2) With a conventional process, as depicted in FIG. 1(A), the        actual mass loadings of the electrodes and the apparent        densities for the active materials are too low to achieve a        gravimetric energy density of >200 Wh/kg. In most cases, the        anode active material mass loading of the electrodes (areal        density) is significantly lower than 25 mg/cm² and the apparent        volume density or tap density of the active material is        typically less than 1.2 g/cm³ even for relatively large        particles of graphite. The cathode active material mass loading        of the electrodes (areal density) is significantly lower than 45        mg/cm² for lithium metal oxide-type inorganic materials and        lower than 15 mg/cm² for organic or polymer materials. In        addition, there are so many other non-active materials (e.g.        conductive additive and resin binder) that add additional        weights and volumes to the electrode without contributing to the        cell capacity. These low areal densities and low volume        densities result in relatively low gravimetric energy density        and low volumetric energy density.    -   3) The conventional process requires dispersing electrode active        materials (anode active material or cathode active material) in        a liquid solvent (e.g. NMP) to make a slurry and, upon coating        on a current collector surface, the liquid solvent has to be        removed to dry the electrode layer. Once the anode and cathode        layers, along with a separator layer, are laminated together and        packaged in a housing to make a supercapacitor cell, one then        injects a liquid electrolyte into the cell. In actuality, one        makes the two electrodes wet, then makes the electrodes dry, and        finally makes them wet again. Such a wet-dry-wet process does        not sound like a good process at all.    -   4) Current lithium-ion batteries still suffer from a relatively        low gravimetric energy density and low volumetric energy        density. Commercially available lithium-ion batteries exhibit a        gravimetric energy density of approximately 150-220 Wh/kg and a        volumetric energy density of 450-600 Wh/L.        -   In literature, the energy density data reported based on            either the active material weight alone or the electrode            weight cannot directly translate into the energy densities            of a practical battery cell or device. The “overhead weight”            or weights of other device components (binder, conductive            additive, current collectors, separator, electrolyte, and            packaging) must also be taken into account. The convention            production process results in the weight proportion of the            anode active material (e.g. graphite or carbon) in a            lithium-ion battery being typically from 12% to 17%, and            that of the cathode active material (e.g. LiMn₂O₄) from 20%            to 35%.

The present invention provides a process for producing an electrode ofan alkali metal battery cell having a high electrode thickness, highactive material mass loading, low overhead weight and volume, highvolumetric capacitance, and high volumetric energy density. In addition,the manufacturing costs of the alkali metal batteries produced by thepresently invented process are significantly lower than those byconventional processes.

In one embodiment of the present invention, as illustrated in FIGS. 1(C)and 1(D), the invented process comprises continuously feeding anelectrically conductive porous layer (e.g. 304, 310, 322, or 330), froma feeder roller (not shown), into an active material impregnation zonewhere a wet active material mixture (e.g. slurry, suspension, orgel-like mass, such as 306 a, 306 b, 312 a, 312 b) of an electrodeactive material and an optional conductive additive is delivered to atleast a porous surface of the porous layer (e.g. 304 or 310 in SchematicA and schematic B, respectively, of FIG. 1(C)). Using Schematic A as anexample, the wet active material mixture (306 a, 306 b) is forced toimpregnate into the porous layer from both sides using one or two pairsof rollers (302 a, 302 b, 302 c, and 302 d) to form an impregnatedactive electrode 308 (an anode or cathode). The conductive porous layercontains interconnected conductive pathways and at least 70% by volume(preferably >80%) of pores.

In Schematic B, two feeder rollers 316 a, 316 b are used to continuouslypay out two protective films 314 a, 314 b that support wet activematerial mixture layers 312 a, 312 b. These wet active material mixturelayers 312 a, 312 b can be delivered to the protective (supporting)films 314 a, 314 b using a broad array of procedures (e.g. printing,spraying, casting, coating, etc., which are well known in the art). Asthe conductive porous layer 110 moves though the gaps between two setsof rollers (318 a, 318 b, 318 c, 318 d), the wet active mixture materialis impregnated into the pores of the porous layer 310 to form an activematerial electrode 320 (an anode or cathode electrode layer) covered bytwo protective films 314 a, 314 b.

Using Schematic C as another example, two spraying devices 324 a, 324 bwere used to dispense the wet active material mixture (325 a, 325 b) tothe two opposed porous surfaces of the conductive porous layer 322. Thewet active material mixture is forced to impregnate into the porouslayer from both sides using one or two pairs of rollers to form animpregnated active electrode 326 (an anode or cathode). Similarly, inSchematic D, two spraying devices 332 a, 332 b were used to dispense thewet active material mixture (333 a, 333 b) to the two opposed poroussurfaces of the conductive porous layer 330. The wet active materialmixture is forced to impregnate into the porous layer from both sidesusing one or two pairs of rollers to form an impregnated activeelectrode 338 (an anode or cathode).

The resulting electrode layer (anode or cathode electrode), afterconsolidation, has a thickness no less than 100 μm (preferably >200 μm,further preferably >300 μm, more preferably >400 μm; further morepreferably >500 μm, 600 μm, or even >1,000 μm; no theoretical limitationon this anode thickness. Consolidation is accomplished with theapplication of a compressive stress (from rollers) to force the wetactive material mixture ingredients to infiltrate into the pores of theconductive porous layer. The conductive porous layer is also compressedtogether to form a current collector that essentially extends over thethickness of the entire electrode.

Another example, as illustrated in Schematic E of FIG. 1(D), theelectrode production process begins by continuously feeding a conductiveporous layer 356 from a feeder roller 340. The porous layer 356 isdirected by a roller 342 to get immersed into a wet active materialmixture mass 346 (slurry, suspension, gel, etc.) in a container 344. Theactive material mixture begins to impregnate into pores of the porouslayer 356 as it travels toward roller 342 b and emerges from thecontainer to feed into the gap between two rollers 348 a, 348 b. Twoprotective films 350 a, 350 b are concurrently fed from two respectiverollers 352 a, 352 b to cover the impregnated porous layer 354, whichmay be continuously collected on a rotating drum (a winding roller 355).The process is applicable to both the anode and the cathode electrodes.

As illustrated in Schematic F of FIG. 1(E), at least one anode electrode364 (e.g. produced by the presently invented process), a porousseparator 366, and at least one cathode electrode 368 (e.g. produced bythe presently invented process), may be unwound from rollers 360 a, 360b, and 360 c, respectively, laminated and consolidated together bymoving through a pair of rollers 362 a, 362 b to form an alkali metalion battery assembly 370. Such a battery assembly 370 can be slit andcut into any desired shape and dimensions and sealed in a protectivehousing. It may be noted that a plurality of impregnated anode layerscan be stacked and compacted into one single anode electrode. Similarly,a plurality of impregnated cathode layers can be stacked and compactedinto one single cathode electrode.

Alternatively, as illustrated in Schematic G of FIG. 1(E), an anodeelectrode 378 (e.g. a Cu foil coated with Li or Na metal on twosurfaces), a porous separator 376, and a cathode electrode 374 (e.g.produced by the presently invented process), may be unwound from rollers370 c, 370 b, and 370 a, respectively, laminated and consolidatedtogether by moving through a pair of rollers 362 a, 362 b to form analkali metal battery assembly 380. Such a battery assembly 380 can beslit and cut into any desired shape and dimensions and sealed in aprotective housing.

The above are but several examples to illustrate how the presentlyinvented alkali metal electrodes and alkali metal batteries can be madecontinuously, in an automated manner. These examples should not be usedto limit the scope of the instant invention.

The electrically conductive porous layers may be selected from metalfoam, metal web or screen, perforated metal sheet-based structure, metalfiber mat, metal nanowire mat, conductive polymer nano-fiber mat,conductive polymer foam, conductive polymer-coated fiber foam, carbonfoam, graphite foam, carbon aerogel, carbon xerox gel, graphene foam,graphene oxide foam, reduced graphene oxide foam, carbon fiber foam,graphite fiber foam, exfoliated graphite foam, or a combination thereof.The porous layers must be made of an electrically conductive material,such as a carbon, graphite, metal, metal-coated fiber, conductivepolymer, or conductive polymer-coated fiber, which is in a form ofhighly porous mat, screen/grid, non-woven, foam, etc. Examples ofconductive porous layers are presented in FIGS. 3(A), 3(B), 3(C), and3(D). The porosity level must be at least 70% by volume, preferablygreater than 80%, further preferably greater than 90%, and mostpreferably greater than 95% by volume. The backbone or foam walls form anetwork of electron-conducting pathways.

Preferably, substantially all of the pores in the original conductiveporous layers are filled with the electrode (anode or cathode) activematerial, optional conductive additive, and liquid electrolyte (nobinder resin needed). Since there are great amounts of pores (80-99%)relative to the pore walls or conductive pathways (1-20%), very littlespace is wasted (“being wasted” means not being occupied by theelectrode active material and electrolyte), resulting in high amounts ofelectrode active material-electrolyte zones (high active materialloading mass).

In such battery electrode configurations (FIG. 1(C)-(E)), the electronsonly have to travel a short distance (half of the pore size, on average;e.g. a few micrometers) before they are collected by the currentcollector (pore walls) since pore walls are present everywherethroughout the entire current collector (also the entire anode layer).These pore walls form a 3-D network of interconnectedelectron-transporting pathways with minimal resistance. Additionally, ineach anode electrode or cathode electrode layer, all electrode activematerial particles are pre-dispersed in a liquid electrolyte (nowettability issue), eliminating the existence of dry pockets commonlypresent in an electrode prepared by the conventional process of wetcoating, drying, packing, and electrolyte injection. Thus, the presentlyinvented process produces a totally unexpected advantage over theconventional battery cell production process.

In a preferred embodiment, the anode active material is a prelithiatedor pre-sodiated version of graphene sheets selected from pristinegraphene, graphene oxide, reduced graphene oxide, graphene fluoride,graphene chloride, graphene bromide, graphene iodide, hydrogenatedgraphene, nitrogenated graphene, chemically functionalized graphene, ora combination thereof. The starting graphitic material for producing anyone of the above graphene materials may be selected from naturalgraphite, artificial graphite, meso-phase carbon, meso-phase pitch,meso-carbon micro-bead, soft carbon, hard carbon, coke, carbon fiber,carbon nano-fiber, carbon nano-tube, or a combination thereof. Graphenematerials are also a good conductive additive for both the anode andcathode active materials of an alkali metal battery.

The constituent graphene planes of a graphite crystallite in a naturalor artificial graphite particle can be exfoliated and extracted orisolated to obtain individual graphene sheets of hexagonal carbon atoms,which are single-atom thick, provided the inter-planar van der Waalsforces can be overcome. An isolated, individual graphene plane of carbonatoms is commonly referred to as single-layer graphene. A stack ofmultiple graphene planes bonded through van der Waals forces in thethickness direction with an inter-graphene plane spacing ofapproximately 0.3354 nm is commonly referred to as a multi-layergraphene. A multi-layer graphene platelet has up to 300 layers ofgraphene planes (<100 nm in thickness), but more typically up to 30graphene planes (<10 nm in thickness), even more typically up to 20graphene planes (<7 nm in thickness), and most typically up to 10graphene planes (commonly referred to as few-layer graphene inscientific community). Single-layer graphene and multi-layer graphenesheets are collectively called “nano graphene platelets” (NGPs).Graphene sheets/platelets (collectively, NGPs) are a new class of carbonnano material (a 2-D nano carbon) that is distinct from the 0-Dfullerene, the 1-D CNT or CNF, and the 3-D graphite. For the purpose ofdefining the claims and as is commonly understood in the art, a graphenematerial (isolated graphene sheets) is not (and does not include) acarbon nanotube (CNT) or a carbon nano-fiber (CNF).

In one process, graphene materials are obtained by intercalating naturalgraphite particles with a strong acid and/or an oxidizing agent toobtain a graphite intercalation compound (GIC) or graphite oxide (GO),as illustrated in FIG. 4(A) and FIG. 4(B) (schematic drawings). Thepresence of chemical species or functional groups in the interstitialspaces between graphene planes in a GIC or GO serves to increase theinter-graphene spacing (d₀₀₂, as determined by X-ray diffraction),thereby significantly reducing the van der Waals forces that otherwisehold graphene planes together along the c-axis direction. The GIC or GOis most often produced by immersing natural graphite powder (100 in FIG.4(B)) in a mixture of sulfuric acid, nitric acid (an oxidizing agent),and another oxidizing agent (e.g. potassium permanganate or sodiumperchlorate). The resulting GIC (102) is actually some type of graphiteoxide (GO) particles if an oxidizing agent is present during theintercalation procedure. This GIC or GO is then repeatedly washed andrinsed in water to remove excess acids, resulting in a graphite oxidesuspension or dispersion, which contains discrete and visuallydiscernible graphite oxide particles dispersed in water. In order toproduce graphene materials, one can follow one of the two processingroutes after this rinsing step, briefly described below:

Route 1 involves removing water from the suspension to obtain“expandable graphite,” which is essentially a mass of dried GIC or driedgraphite oxide particles. Upon exposure of expandable graphite to atemperature in the range of typically 800-1,050° C. for approximately 30seconds to 2 minutes, the GIC undergoes a rapid volume expansion by afactor of 30-300 to form “graphite worms” (104), which are each acollection of exfoliated, but largely un-separated graphite flakes thatremain interconnected.

In Route 1A, these graphite worms (exfoliated graphite or “networks ofinterconnected/non-separated graphite flakes”) can be re-compressed toobtain flexible graphite sheets or foils (106) that typically have athickness in the range of 0.1 mm (100 μm)-0.5 mm (500 μm).Alternatively, one may choose to use a low-intensity air mill orshearing machine to simply break up the graphite worms for the purposeof producing the so-called “expanded graphite flakes” (108) whichcontain mostly graphite flakes or platelets thicker than 100 nm (hence,not a nano material by definition).

In Route 1B, the exfoliated graphite is subjected to high-intensitymechanical shearing (e.g. using an ultrasonicator, high-shear mixer,high-intensity air jet mill, or high-energy ball mill) to form separatedsingle-layer and multi-layer graphene sheets (collectively called NGPs,112), as disclosed in our U.S. application Ser. No. 10/858,814 (Jun. 3,2004). Single-layer graphene can be as thin as 0.34 nm, whilemulti-layer graphene can have a thickness up to 100 nm, but moretypically less than 10 nm (commonly referred to as few-layer graphene).Multiple graphene sheets or platelets may be made into a sheet of NGPpaper using a paper-making process. This sheet of NGP paper is anexample of the porous graphene structure layer utilized in the presentlyinvented process.

Route 2 entails ultrasonicating the graphite oxide suspension (e.g.graphite oxide particles dispersed in water) for the purpose ofseparating/isolating individual graphene oxide sheets from graphiteoxide particles. This is based on the notion that the inter-grapheneplane separation bas been increased from 0.3354 nm in natural graphiteto 0.6-1.1 nm in highly oxidized graphite oxide, significantly weakeningthe van der Waals forces that hold neighboring planes together.Ultrasonic power can be sufficient to further separate graphene planesheets to form fully separated, isolated, or discrete graphene oxide(GO) sheets. These graphene oxide sheets can then be chemically orthermally reduced to obtain “reduced graphene oxides” (RGO) typicallyhaving an oxygen content of 0.001%-10% by weight, more typically0.01%-5% by weight, most typically and preferably less than 2% by weightof oxygen.

For the purpose of defining the claims of the instant application, NGPsor graphene materials include discrete sheets/platelets of single-layerand multi-layer (typically less than 10 layers) pristine graphene,graphene oxide, reduced graphene oxide (RGO), graphene fluoride,graphene chloride, graphene bromide, graphene iodide, hydrogenatedgraphene, nitrogenated graphene, chemically functionalized graphene,doped graphene (e.g. doped by B or N). Pristine graphene has essentially0% oxygen. RGO typically has an oxygen content of 0.001%-5% by weight.Graphene oxide (including RGO) can have 0.001%-50% by weight of oxygen.Other than pristine graphene, all the graphene materials have 0.001%-50%by weight of non-carbon elements (e.g. O, H, N, B, F, Cl, Br, I, etc.).These materials are herein referred to as non-pristine graphenematerials.

Pristine graphene, in smaller discrete graphene sheets (typically 0.3 μmto 10 μm), may be produced by direct ultrasonication (also known asliquid phase exfoliation or production) or supercritical fluidexfoliation of graphite particles. These processes are well-known in theart.

The graphene oxide (GO) may be obtained by immersing powders orfilaments of a starting graphitic material (e.g. natural graphitepowder) in an oxidizing liquid medium (e.g. a mixture of sulfuric acid,nitric acid, and potassium permanganate) in a reaction vessel at adesired temperature for a period of time (typically from 0.5 to 96hours, depending upon the nature of the starting material and the typeof oxidizing agent used). As previously described above, the resultinggraphite oxide particles may then be subjected to thermal exfoliation orultrasonic wave-induced exfoliation to produce isolated GO sheets. TheseGO sheets can then be converted into various graphene materials bysubstituting —OH groups with other chemical groups (e.g. —Br, NH₂,etc.).

Fluorinated graphene or graphene fluoride is herein used as an exampleof the halogenated graphene material group. There are two differentapproaches that have been followed to produce fluorinated graphene: (1)fluorination of pre-synthesized graphene: This approach entails treatinggraphene prepared by mechanical exfoliation or by CVD growth withfluorinating agent such as XeF₂, or F-based plasmas; (2) Exfoliation ofmultilayered graphite fluorides: Both mechanical exfoliation and liquidphase exfoliation of graphite fluoride can be readily accomplished.

Interaction of F₂ with graphite at high temperature leads to covalentgraphite fluorides (CF)_(n) or (C₂F)_(n), while at low temperaturesgraphite intercalation compounds (GIC) C_(x)F (2≦x≦24) form. In (CF)_(n)carbon atoms are sp3-hybridized and thus the fluorocarbon layers arecorrugated consisting of trans-linked cyclohexane chairs. In (C₂F)_(n)only half of the C atoms are fluorinated and every pair of the adjacentcarbon sheets are linked together by covalent C—C bonds. Systematicstudies on the fluorination reaction showed that the resulting F/C ratiois largely dependent on the fluorination temperature, the partialpressure of the fluorine in the fluorinating gas, and physicalcharacteristics of the graphite precursor, including the degree ofgraphitization, particle size, and specific surface area. In addition tofluorine (F₂), other fluorinating agents may be used, although most ofthe available literature involves fluorination with F₂ gas, sometimes inpresence of fluorides.

For exfoliating a layered precursor material to the state of individuallayers or few-layers, it is necessary to overcome the attractive forcesbetween adjacent layers and to further stabilize the layers. This may beachieved by either covalent modification of the graphene surface byfunctional groups or by non-covalent modification using specificsolvents, surfactants, polymers, or donor-acceptor aromatic molecules.The process of liquid phase exfoliation includes ultra-sonic treatmentof a graphite fluoride in a liquid medium.

The nitrogenation of graphene can be conducted by exposing a graphenematerial, such as graphene oxide, to ammonia at high temperatures(200-400° C.). Nitrogenated graphene could also be formed at lowertemperatures by a hydrothermal method; e.g. by sealing GO and ammonia inan autoclave and then increased the temperature to 150-250° C. Othermethods to synthesize nitrogen doped graphene include nitrogen plasmatreatment on graphene, arc-discharge between graphite electrodes in thepresence of ammonia, ammonolysis of graphene oxide under CVD conditions,and hydrothermal treatment of graphene oxide and urea at differenttemperatures.

The aforementioned features are further described and explained indetail as follows: As illustrated in FIG. 4(B), a graphite particle(e.g. 100) is typically composed of multiple graphite crystallites orgrains. A graphite crystallite is made up of layer planes of hexagonalnetworks of carbon atoms. These layer planes of hexagonally arrangedcarbon atoms are substantially flat and are oriented or ordered so as tobe substantially parallel and equidistant to one another in a particularcrystallite. These layers of hexagonal-structured carbon atoms, commonlyreferred to as graphene layers or basal planes, are weakly bondedtogether in their thickness direction (crystallographic c-axisdirection) by weak van der Waals forces and groups of these graphenelayers are arranged in crystallites. The graphite crystallite structureis usually characterized in terms of two axes or directions: the c-axisdirection and the a-axis (or b-axis) direction. The c-axis is thedirection perpendicular to the basal planes. The a- or b-axes are thedirections parallel to the basal planes (perpendicular to the c-axisdirection).

Due to the weak van der Waals forces holding the parallel graphenelayers, natural graphite can be treated so that the spacing between thegraphene layers can be appreciably opened up so as to provide a markedexpansion in the c-axis direction, and thus form an expanded graphitestructure in which the laminar character of the carbon layers issubstantially retained. The process for manufacturing flexible graphiteis well-known in the art. In general, flakes of natural graphite (e.g.100 in FIG. 4(B)) are intercalated in an acid solution to producegraphite intercalation compounds (GICs, 102). The GICs are washed,dried, and then exfoliated by exposure to a high temperature for a shortperiod of time. This causes the flakes to expand or exfoliate in thec-axis direction of the graphite up to 80-300 times of their originaldimensions. The exfoliated graphite flakes are vermiform in appearanceand, hence, are commonly referred to as graphite worms 104. These wormsof graphite flakes which have been greatly expanded can be formedwithout the use of a binder into cohesive or integrated sheets ofexpanded graphite, e.g. webs, papers, strips, tapes, foils, mats or thelike (typically referred to as “flexible graphite” 106) having a typicaldensity of about 0.04-2.0 g/cm³ for most applications.

Acids, such as sulfuric acid, are not the only type of intercalatingagent (intercalant) that penetrate into spaces between graphene planesto obtain GICs. Many other types of intercalating agents, such as alkalimetals (Li, K, Na, Cs, and their alloys or eutectics), can be used tointercalate graphite to stage 1, stage 2, stage 3, etc. Stage n impliesone intercalant layer for every n graphene planes. For instance, astage-1 potassium-intercalated GIC means there is one layer of K forevery graphene plane; or, one can find one layer of K atoms insertedbetween two adjacent graphene planes in a G/K/G/K/G/KG . . . sequence,where G is a graphene plane and K is a potassium atom plane. A stage-2GIC will have a sequence of GG/K/GG/K/GG/K/GG . . . and a stage-3 GICwill have a sequence of GGG/K/GGG/K/GGG . . . , etc. These GICs can thenbe brought in contact with water or water-alcohol mixture to produceexfoliated graphite and/or separated/isolated graphene sheets.

Exfoliated graphite worms may be subjected to high-intensity mechanicalshearing/separation treatments using a high-intensity air jet mill,high-intensity ball mill, or ultrasonic device to produce separated nanographene platelets (NGPs) with all the graphene platelets thinner than100 nm, mostly thinner than 10 nm, and, in many cases, beingsingle-layer graphene (also illustrated as 112 in FIG. 4(B)). An NGP iscomposed of a graphene sheet or a plurality of graphene sheets with eachsheet being a two-dimensional, hexagonal structure of carbon atoms. Amass of multiple NGPs (including discrete sheets/platelets ofsingle-layer and/or few-layer graphene or graphene oxide may be madeinto a porous graphene film (114 in FIG. 4(B)) using a film-makingprocess. Alternatively, with a low-intensity shearing, graphite wormstend to be separated into the so-called expanded graphite flakes (108 inFIG. 4(B) having a thickness>100 nm. These flakes can be formed intographite mat or nonwoven 106 using mat-making process, with or without aresin binder, to form an expanded graphite foam. Graphite foams can bemade by graphitization of carbon foams as well.

There is no restriction on the types of anode active materials orcathode active materials that can be used in practicing the instantinvention. Preferably, in the invented process, the anode activematerial absorbs alkali ions (e.g. lithium ions) at an electrochemicalpotential of less than 1.0 volt (preferably less than 0.7 volts) abovethe Li/Li⁺ (i.e. relative to Li→Li⁺+e⁻ as the standard potential) theNa/Na⁺ reference when the battery is charged. In one preferredembodiment, the anode active material is selected from the groupconsisting of: (a) Particles of natural graphite, artificial graphite,meso-carbon microbeads (MCMB), and carbon (including soft carbon, hardcarbon, carbon nano-fiber, and carbon nano-tube); (b) Silicon (Si),germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc(Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium(Ti), iron (Fe), and cadmium (Cd); (Si, Ge, Al, and Sn are mostdesirable due to their high specific capacities.) (c) Alloys orintermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd withother elements, wherein the alloys or compounds are stoichiometric ornon-stoichiometric (e.g. SiAl, SiSn); (d) Oxides, carbides, nitrides,sulfides, phosphides, selenides, and tellurides of Si, Ge, Sn, Pb, Sb,Bi, Zn, Al, Fe, Ni, Co, Ti, Mn, or Cd, and their mixtures or composites(e.g. SnO, TiO₂, Co₃O₄, etc.); (e) Pre-lithiated versions thereof (e.g.pre-lithiated TiO₂, which is lithium titanate); (f) Pre-lithiatedgraphene sheets; and combinations thereof.

In another preferred embodiment, the anode active material is apre-sodiated or pre-potassiated version of graphene sheets selected frompristine graphene, graphene oxide, reduced graphene oxide, graphenefluoride, graphene chloride, graphene bromide, graphene iodide,hydrogenated graphene, nitrogenated graphene, chemically functionalizedgraphene, or a combination thereof. The starting graphitic material forproducing any one of the above graphene materials may be selected fromnatural graphite, artificial graphite, meso-phase carbon, meso-phasepitch, meso-carbon micro-bead, soft carbon, hard carbon, coke, carbonfiber, carbon nano-fiber, carbon nano-tube, or a combination thereof.Graphene materials are also a good conductive additive for both theanode and cathode active materials of an alkali metal battery.

In the rechargeable alkali metal battery, the anode may contain analkali ion source selected from an alkali metal, an alkali metal alloy,a mixture of alkali metal or alkali metal alloy with an alkaliintercalation compound, an alkali element-containing compound, or acombination thereof. Particularly desired is an anode active materialthat contains an alkali intercalation compound selected from petroleumcoke, carbon black, amorphous carbon, hard carbon, templated carbon,hollow carbon nanowires, hollow carbon sphere, titanates, NaTi₂(PO₄)₃,Na₂Ti₃O₇ (Sodium titanate), Na₂C₈H₄O₄ (Disodium Terephthalate), Na₂TP(Sodium Terephthalate), TiO₂, Na_(x)TiO₂ (x=0.2 to 1.0), carboxylatebased materials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄, C₁₀H₂Na₄O₈,C₁₄H₄O₆, C₁₄H₄Na₄O₈, or a combination thereof.

In an embodiment, the anode may contain a mixture of 2 or 3 types ofanode active materials (e.g. mixed particles of activatedcarbon+NaTi₂(PO₄)₃) and the cathode can be a sodium intercalationcompound alone (e.g. Na_(x)MnO₂), an electric double layercapacitor-type cathode active material alone (e.g. activated carbon), aredox pair of λ-MnO₂/activated carbon for pseudo-capacitance.

A wide variety of cathode active materials can be used to practice thepresently invented process. The cathode active material typically is analkali metal intercalation compound or alkali metal-absorbing compoundthat is capable of storing alkali metal ions when the battery isdischarged and releasing alkali metal ions into the electrolyte whenrec-charged. The cathode active material may be selected from aninorganic material, an organic or polymeric material, a metaloxide/phosphate/sulfide (most desired types of inorganic cathodematerials), or a combination thereof.

The group of metal oxide, metal phosphate, and metal sulfides consistingof lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide,lithium vanadium oxide, lithium transition metal oxide, lithium-mixedmetal oxide, lithium iron phosphate, lithium manganese phosphate,lithium vanadium phosphate, lithium mixed metal phosphates, transitionmetal sulfides, and combinations thereof. In particular, the lithiumvanadium oxide may be selected from the group consisting of VO₂,Li_(x)VO₂, V₂O₅, Li_(x)V₂O₅, V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉,Li_(x)V₄O₉, V₆O₁₃, Li_(x)V₆O₁₃, their doped versions, their derivatives,and combinations thereof, wherein 0.1<x<5. Lithium transition metaloxide may be selected from a layered compound LiMO₂, spinel compoundLiM₂O₄, olivine compound LiMPO₄, silicate compound Li₂MSiO₄, Tavoritecompound LiMPO₄F, borate compound LiMBO₃, or a combination thereof,wherein M is a transition metal or a mixture of multiple transitionmetals.

In the alkali metal cell or alkali metal-ion cell, the cathode activematerial may contain a sodium intercalation compound (or their potassiumcounterparts) selected from NaFePO₄ (Sodium iron phosphate),Na_(0.7)FePO₄, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V2(PO₄)₂F₃,Na₂FePO₄F, NaFeF₃, NaVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5),Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂ (Sodiumcobalt oxide), Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂,Na_(x)MnO₂ (Sodium manganese bronze), λ-MnO₂, Na_(0.44)MnO₂,Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈, NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇,Ni_(1/3)Mn_(1/3)Co_(1/3)O₂, Cu_(0.56)Ni_(0.44)HCF (Copper and nickelhexacyanoferrate), NiHCF (nickel hexacyanoferrate), Na_(x)CoO₂, NaCrO₂,Na₃Ti₂(PO₄)₃, NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C,NaV_(1-x)Cr_(x)PO₄F, Se_(y)S_(z) (Selenium and Selenium/Sulfur, z/y from0.01 to 100), Se (without S), Alluaudites, or a combination thereof.

Other inorganic materials for use as a cathode active material may beselected from sulfur, sulfur compound, lithium polysulfide, transitionmetal dichalcogenide, a transition metal trichalcogenide, or acombination thereof. In particular, the inorganic material is selectedfrom TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂, an iron oxide, a vanadiumoxide, or a combination thereof. These will be further discussed later.

In particular, the inorganic material may be selected from: (a) bismuthselenide or bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof.

Alternatively, the cathode active material may be selected from afunctional material or nano-structured material having an alkali metalion-capturing functional group or alkali metal ion-storing surface indirect contact with the electrolyte. Preferably, the functional groupreversibly reacts with an alkali metal ion, forms a redox pair with analkali metal ion, or forms a chemical complex with an alkali metal ion.The functional material or nano-structured material may be selected fromthe group consisting of (a) a nano-structured or porous disorderedcarbon material selected from a soft carbon, hard carbon, polymericcarbon or carbonized resin, meso-phase carbon, coke, carbonized pitch,carbon black, activated carbon, nano-cellular carbon foam or partiallygraphitized carbon; (b) a nano graphene platelet selected from asingle-layer graphene sheet or multi-layer graphene platelet; (c) acarbon nanotube selected from a single-walled carbon nanotube ormulti-walled carbon nanotube; (d) a carbon nano-fiber, nano-wire, metaloxide nano-wire or fiber, conductive polymer nano-fiber, or acombination thereof; (e) a carbonyl-containing organic or polymericmolecule; (f) a functional material containing a carbonyl, carboxylic,or amine group; and combinations thereof.

The functional material or nano-structured material may be selected fromthe group consisting ofPoly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene), Na_(x)C₆O₆ (x=1-3),Na₂(C₆H₂O₄), Na₂C₈H₄O₄ (Na terephthalate), Na₂C₆H₄O₄ (Litrans-trans-muconate), 3,4,9,10-perylenetetracarboxylicacid-dianhydride(PTCDA) sulfide polymer, PTCDA,1,4,5,8-naphthalene-tetracarboxylicacid-dianhydride (NTCDA),Benzene-1,2,4,5-tetracarboxylic dianhydride, 1,4,5,8-tetrahydroxyanthraquinon, Tetrahydroxy-p-benzoquinone, and combinations thereof.Desirably, the functional material or nano-structured material has afunctional group selected from —COOH, ═O, —NH₂, —OR, or —COOR, where Ris a hydrocarbon radical.

The organic material or polymeric material may be selected fromPoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).

The organic material may be selected from a phthalocyanine compoundselected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.

The lithium intercalation compound or lithium-absorbing compound may beselected from a metal carbide, metal nitride, metal boride, metaldichalcogenide, or a combination thereof. Preferably, the lithiumintercalation compound or lithium-absorbing compound is selected from anoxide, dichalcogenide, trichalcogenide, sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in ananowire, nano-disc, nano-ribbon, or nano platelet form.

We have discovered that a wide variety of two-dimensional (2D) inorganicmaterials can be used as a cathode active material in the presentedinvented lithium battery prepared by the invented direct activematerial-electrolyte injection process. Layered materials represent adiverse source of 2D systems that can exhibit unexpected electronicproperties and good affinity to lithium ions. Although graphite is thebest known layered material, transition metal dichalcogenides (TMDs),transition metal oxides (TMOs), and a broad array of other compounds,such as BN, Bi₂Te₃, and Bi₂Se₃, are also potential sources of 2Dmaterials.

Preferably, the lithium intercalation compound or lithium-absorbingcompound is selected from nano discs, nano platelets, nano-coating, ornano sheets of an inorganic material selected from: (a) bismuth selenideor bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof; wherein the discs, platelets, or sheets havea thickness less than 100 nm. The lithium intercalation compound orlithium-absorbing compound may contain nano discs, nano platelets,nano-coating, or nano sheets of a compound selected from: (i) bismuthselenide or bismuth telluride, (ii) transition metal dichalcogenide ortrichalcogenide, (iii) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (iv) boron nitride, or(v) a combination thereof, wherein the discs, platelets, coating, orsheets have a thickness less than 100 nm.

Non-graphene 2D nano materials, single-layer or few-layer (up to 20layers), can be produced by several methods: mechanical cleavage, laserablation (e.g. using laser pulses to ablate TMDs down to a singlelayer), liquid phase exfoliation, and synthesis by thin film techniques,such as PVD (e.g. sputtering), evaporation, vapor phase epitaxy, liquidphase epitaxy, chemical vapor epitaxy, molecular beam epitaxy (MBE),atomic layer epitaxy (ALE), and their plasma-assisted versions.

A wide range of electrolytes can be used for practicing the instantinvention. Most preferred are non-aqueous organic and/or ionic liquidelectrolytes. The non-aqueous electrolyte to be employed herein may beproduced by dissolving an electrolytic salt in a non-aqueous solvent.Any known non-aqueous solvent which has been employed as a solvent for alithium secondary battery can be employed. A non-aqueous solvent mainlyconsisting of a mixed solvent comprising ethylene carbonate (EC) and atleast one kind of non-aqueous solvent whose melting point is lower thanthat of aforementioned ethylene carbonate and whose donor number is 18or less (hereinafter referred to as a second solvent) may be preferablyemployed. This non-aqueous solvent is advantageous in that it is (a)stable against a negative electrode containing a carbonaceous materialwell developed in graphite structure; (b) effective in suppressing thereductive or oxidative decomposition of electrolyte; and (c) high inconductivity. A non-aqueous electrolyte solely composed of ethylenecarbonate (EC) is advantageous in that it is relatively stable againstdecomposition through a reduction by a graphitized carbonaceousmaterial. However, the melting point of EC is relatively high, 39 to 40°C., and the viscosity thereof is relatively high, so that theconductivity thereof is low, thus making EC alone unsuited for use as asecondary battery electrolyte to be operated at room temperature orlower. The second solvent to be used in a mixture with EC functions tomake the viscosity of the solvent mixture lower than that of EC alone,thereby promoting the ion conductivity of the mixed solvent.Furthermore, when the second solvent having a donor number of 18 or less(the donor number of ethylene carbonate is 16.4) is employed, theaforementioned ethylene carbonate can be easily and selectively solvatedwith lithium ion, so that the reduction reaction of the second solventwith the carbonaceous material well developed in graphitization isassumed to be suppressed. Further, when the donor number of the secondsolvent is controlled to not more than 18, the oxidative decompositionpotential to the lithium electrode can be easily increased to 4 V ormore, so that it is possible to manufacture a lithium secondary batteryof high voltage.

Preferable second solvents are dimethyl carbonate (DMC), methylethylcarbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methylpropionate, propylene carbonate (PC), .gamma.-butyrolactone(.gamma.-BL), acetonitrile (AN), ethyl acetate (EA), propyl formate(PF), methyl formate (MF), toluene, xylene and methyl acetate (MA).These second solvents may be employed singly or in a combination of twoor more. More desirably, this second solvent should be selected fromthose having a donor number of 16.5 or less. The viscosity of thissecond solvent should preferably be 28 cps or less at 25° C.

The mixing ratio of the aforementioned ethylene carbonate in the mixedsolvent should preferably be 10 to 80% by volume. If the mixing ratio ofthe ethylene carbonate falls outside this range, the conductivity of thesolvent may be lowered or the solvent tends to be more easilydecomposed, thereby deteriorating the charge/discharge efficiency. Morepreferable mixing ratio of the ethylene carbonate is 20 to 75% byvolume. When the mixing ratio of ethylene carbonate in a non-aqueoussolvent is increased to 20% by volume or more, the solvating effect ofethylene carbonate to lithium ions will be facilitated and the solventdecomposition-inhibiting effect thereof can be improved.

Examples of preferred mixed solvent are a composition comprising EC andMEC; comprising EC, PC and MEC; comprising EC, MEC and DEC; comprisingEC, MEC and DMC; and comprising EC, MEC, PC and DEC; with the volumeratio of MEC being controlled within the range of 30 to 80%. Byselecting the volume ratio of MEC from the range of 30 to 80%, morepreferably 40 to 70%, the conductivity of the solvent can be improved.With the purpose of suppressing the decomposition reaction of thesolvent, an electrolyte having carbon dioxide dissolved therein may beemployed, thereby effectively improving both the capacity and cycle lifeof the battery. The electrolytic salts to be incorporated into anon-aqueous electrolyte may be selected from a lithium salt such aslithium perchlorate (LiClO₄), lithium hexafluorophosphate (LiPF₆),lithium borofluoride (LiBF₄), lithium hexafluoroarsenide (LiAsF₆),lithium trifluoro-metasulfonate (LiCF₃SO₃) and bis-trifluoromethylsulfonylimide lithium [LiN(CF₃SO₂)₂]. Among them, LiPF₆, LiBF₄ andLiN(CF₃SO₂)₂ are preferred. The content of aforementioned electrolyticsalts in the non-aqueous solvent is preferably 0.5 to 2.0 mol/l.

The ionic liquid is composed of ions only. Ionic liquids are low meltingtemperature salts that are in a molten or liquid state when above adesired temperature. For instance, a salt is considered as an ionicliquid if its melting point is below 100° C. If the melting temperatureis equal to or lower than room temperature (25° C.), the salt isreferred to as a room temperature ionic liquid (RTIL). The IL salts arecharacterized by weak interactions, due to the combination of a largecation and a charge-delocalized anion. This results in a low tendency tocrystallize due to flexibility (anion) and asymmetry (cation).

A typical and well-known ionic liquid is formed by the combination of a1-ethyl-3-methylimidazolium (EMI) cation and anN,N-bis(trifluoromethane)sulphonamide (TFSI) anion. This combinationgives a fluid with an ionic conductivity comparable to many organicelectrolyte solutions and a low decomposition propensity and low vaporpressure up to ˜300-400° C. This implies a generally low volatility andnon-flammability and, hence, a much safer electrolyte for batteries.

Ionic liquids are basically composed of organic ions that come in anessentially unlimited number of structural variations owing to thepreparation ease of a large variety of their components. Thus, variouskinds of salts can be used to design the ionic liquid that has thedesired properties for a given application. These include, among others,imidazolium, pyrrolidinium and quaternary ammonium salts as cations andbis(trifluoromethanesulphonyl) imide, bis(fluorosulphonyl)imide, andhexafluorophosphate as anions. Based on their compositions, ionicliquids come in different classes that basically include aprotic, proticand zwitterionic types, each one suitable for a specific application.

Common cations of room temperature ionic liquids (RTILs) include, butnot limited to, tetraalkylammonium, di-, tri-, andtetra-alkylimidazolium, alkylpyridinium, dialkylpyrrolidinium,dialkylpiperidinium, tetraalkylphosphonium, and trialkylsulfonium.Common anions of RTILs include, but not limited to, BF₄ ⁻, B(CN)₄ ⁻,CH₃BF₃ ⁻, CH2CHBF₃ ⁻, CF₃BF₃ ⁻, C₂F₅BF₃ ⁻, n-C₃F₇BF₃ ⁻, n-C₄F₉BF₃ ⁻, PF₆⁻, CF₃CO₂ ⁻, CF₃SO₃ ⁻, N(SO₂CF₃)₂ ⁻, N(COCF₃)(SO₂CF₃)⁻, N(SO₂F)₂ ⁻,N(CN)₂ ⁻, C(CN)₃ ⁻, SCN⁻, SeCN⁻, CuCl₂ ⁻, AlCl₄ ⁻, F(HF)_(2.3) ⁻, etc.Relatively speaking, the combination of imidazolium- or sulfonium-basedcations and complex halide anions such as AlCl₄ ⁻, BF₄ ⁻, CF₃CO₂ ⁻,CF₃SO₃ ⁻, NTf₂ ⁻, N(SO₂F)₂ ⁻, or F(HF)_(2.3) ⁻ results in RTILs withgood working conductivities.

RTILs can possess archetypical properties such as high intrinsic ionicconductivity, high thermal stability, low volatility, low (practicallyzero) vapor pressure, non-flammability, the ability to remain liquid ata wide range of temperatures above and below room temperature, highpolarity, high viscosity, and wide electrochemical windows. Theseproperties, except for the high viscosity, are desirable attributes whenit comes to using an RTIL as an electrolyte ingredient (a salt and/or asolvent) in a supercapacitor.

In what follows, we provide examples for a large number of differenttypes of anode active materials, cathode active materials, andconductive porous layers (e.g. graphite foam, graphene foam, and metalfoam) to illustrate the best mode of practicing the instant invention.Theses illustrative examples and other portions of instant specificationand drawings, separately or in combinations, are more than adequate toenable a person of ordinary skill in the art to practice the instantinvention. However, these examples should not be construed as limitingthe scope of instant invention.

EXAMPLE 1 Illustrative Examples of Electronically Conductive PorousLayers as a Porous Building Block for Current Collectors

Various types of metal foams and fine metal webs/screens arecommercially available for use as conductive porous layers in an anodeor cathode (serving as a current collector); e.g. Ni foam, Cu foam, Alfoam, Ti foam, Ni mesh/web, stainless steel fiber mesh, etc.Metal-coated polymer foams and carbon foams are also used as currentcollectors. The most desirable thickness ranges for these conductiveporous layers are 50-1000 μm, preferably 100-800 μm, more preferably200-600 μm.

EXAMPLE 2 Ni Foam and CVD Graphene Foam-Based Porous Layers Supported onNi Foam Templates

The procedure for producing CVD graphene foam was adapted from thatdisclosed in open literature: Chen, Z. et al. “Three-dimensionalflexible and conductive interconnected graphene networks grown bychemical vapor deposition,” Nature Materials, 10, 424-428 (2011). Nickelfoam, a porous structure with an interconnected 3D scaffold of nickelwas chosen as a template for the growth of graphene foam. Briefly,carbon was introduced into a nickel foam by decomposing CH₄ at 1,000° C.under ambient pressure, and graphene films were then deposited on thesurface of the nickel foam. Due to the difference in the thermalexpansion coefficients between nickel and graphene, ripples and wrinkleswere formed on the graphene films. Four types of foams made in thisexample were used as a current collector in the presently inventedlithium batteries: Ni foam, CVD graphene-coated Ni form, CVD graphenefoam (Ni being etched away), and conductive polymer bonded CVD graphenefoam.

In order to recover (separate) graphene foam from the supporting Nifoam, Ni frame was etched away. In the procedure proposed by Chen, etal., before etching away the nickel skeleton by a hot HCl (or FeCl₃)solution, a thin layer of poly (methyl methacrylate) (PMMA) wasdeposited on the surface of the graphene films as a support to preventthe graphene network from collapsing during nickel etching. After thePMMA layer was carefully removed by hot acetone, a fragile graphene foamsample was obtained. The use of the PMMA support layer was consideredcritical to preparing a free-standing film of graphene foam. Instead, aconducting polymer was used as a binder resin to hold graphene togetherwhile Ni was etched away. The graphene foam or Ni foam thickness rangewas from 35 μm to 600 μm.

The layers of Ni foam or the CVD graphene foam used herein is intendedas conductive porous layers (CPL) to accommodate the ingredients (anodeor cathode active material+optional conductive additive+liquidelectrolyte) for the anode or cathode or both. For instance, Si nanoparticles dispersed in an organic liquid electrolyte (e.g. 1-4.0 M ofLiPF₆ dissolved in PC-EC) were made into gel-like mass, which wasdelivered to a porous surface of a Ni foam continuously fed from afeeder roller to make an anode electrode roller (as in Schematic A ofFIG. 1(C)).

Graphene-supported LFP nano particles dispersed in the same liquidelectrolyte were made into cathode slurry, which was sprayed over twoporous surfaces of a continuous Ni foam layer to form a cathodeelectrode. The Si nano particle-based anode layer, a porous separatorlayer, and a LFP-based cathode layer were then stacked together to forma lithium-ion battery laminate.

EXAMPLE 3 Graphitic Foam-Based Conductive Porous Layers from Pitch-BasedCarbon Foams

Pitch powder, granules, or pellets are placed in a aluminum mold withthe desired final shape of the foam. Mitsubishi ARA-24 meso-phase pitchwas utilized. The sample is evacuated to less than 1 torr and thenheated to a temperature approximately 300° C. At this point, the vacuumwas released to a nitrogen blanket and then a pressure of up to 1,000psi was applied. The temperature of the system was then raised to 800°C. This was performed at a rate of 2 degree C./min. The temperature washeld for at least 15 minutes to achieve a soak and then the furnacepower was turned off and cooled to room temperature at a rate ofapproximately 1.5 degree C./min with release of pressure at a rate ofapproximately 2 psi/min. Final foam temperatures were 630° C. and 800°C. During the cooling cycle, pressure is released gradually toatmospheric conditions. The foam was then heat treated to 1050° C.(carbonized) under a nitrogen blanket and then heat treated in separateruns in a graphite crucible to 2500° C. and 2800° C. (graphitized) inArgon. The graphite foam layers are available in a thickness range of75-500 μm.

EXAMPLE 4 Preparation of Graphene Oxide (GO) and Reduced Graphene Oxide(RGO) Nano Sheets from Natural Graphite Powder

Natural graphite from Huadong Graphite Co. (Qingdao, China) was used asthe starting material. GO was obtained by following the well-knownmodified Hummers method, which involved two oxidation stages. In atypical procedure, the first oxidation was achieved in the followingconditions: 1100 mg of graphite was placed in a 1000 mL boiling flask.Then, 20 g of K₂S₂O₈, 20 g of P₂O₅, and 400 mL of a concentrated aqueoussolution of H₂SO₄ (96%) were added in the flask. The mixture was heatedunder reflux for 6 hours and then let without disturbing for 20 hours atroom temperature. Oxidized graphite was filtered and rinsed withabundant distilled water until neutral pH. A wet cake-like material wasrecovered at the end of this first oxidation.

For the second oxidation process, the previously collected wet cake wasplaced in a boiling flask that contains 69 mL of a concentrated aqueoussolution of H₂SO₄ (96%). The flask was kept in an ice bath as 9 g ofKMnO₄ was slowly added. Care was taken to avoid overheating. Theresulting mixture was stirred at 35° C. for 2 hours (the sample colorturning dark green), followed by the addition of 140 mL of water. After15 min, the reaction was halted by adding 420 mL of water and 15 mL ofan aqueous solution of 30 wt % H₂O₂. The color of the sample at thisstage turned bright yellow. To remove the metallic ions, the mixture wasfiltered and rinsed with a 1:10 HCl aqueous solution. The collectedmaterial was gently centrifuged at 2700 g and rinsed with deionizedwater. The final product was a wet cake that contained 1.4 wt % of GO,as estimated from dry extracts. Subsequently, liquid dispersions of GOplatelets were obtained by lightly sonicating wet-cake materials, whichwere diluted in deionized water.

Surfactant-stabilized RGO (RGO-BS) was obtained by diluting the wet-cakein an aqueous solution of surfactants instead of pure water. Acommercially available mixture of cholate sodium (50 wt. %) anddeoxycholate sodium (50 wt. %) salts provided by Sigma Aldrich was used.The surfactant weight fraction was 0.5 wt. %. This fraction was keptconstant for all samples. Sonication was performed using a BransonSonifier S-250A equipped with a 13 mm step disruptor horn and a 3 mmtapered micro-tip, operating at a 20 kHz frequency. For instance, 10 mLof aqueous solutions containing 0.1 wt. % of GO was sonicated for 10 minand subsequently centrifuged at 2700 g for 30 min to remove anynon-dissolved large particles, aggregates, and impurities. Chemicalreduction of as-obtained GO to yield RGO was conducted by following themethod, which involved placing 10 mL of a 0.1 wt. % GO aqueous solutionin a boiling flask of 50 mL. Then, 10 μL of a 35 wt. % aqueous solutionof N₂H₄ (hydrazine) and 70 mL of a 28 wt. % of an aqueous solution ofNH₄OH (ammonia) were added to the mixture, which was stabilized bysurfactants. The solution was heated to 90° C. and refluxed for 1 h. ThepH value measured after the reaction was approximately 9. The color ofthe sample turned dark black during the reduction reaction.

RGO was used as a conductive additive in either or both of the anode andcathode active material in certain lithium batteries presently invented.Pre-lithiated RGO (e.g. RGO+lithium particles or RGO pre-deposited withlithium coating) was also used as an anode active material that wasmixed with a liquid electrolyte to form wet anode active materialmixtures for selected lithium-ion cells. Selected cathode activematerials (TiS₂ nano particles and LiCoO₂ particles, respectively) andnon-lithiated RGO sheets were dispersed in a liquid electrolyte toprepare wet cathode active material mixture. The wet anode activemixture and cathode active mixtures were delivered to surfaces ofgraphite foams for forming an anode layer and a cathode layer,respectively.

For comparison purposes, slurry coating and drying procedures wereconducted to produce conventional electrodes. Electrodes and a separatordisposed between two dried electrodes were then assembled and encased inan Al-plastic laminated packaging envelop, followed by liquidelectrolyte injection to form a lithium battery cell.

EXAMPLE 5 Preparation of Pristine Graphene Sheets (0% Oxygen)

Recognizing the possibility of the high defect population in GO sheetsacting to reduce the conductivity of individual graphene plane, wedecided to study if the use of pristine graphene sheets (non-oxidizedand oxygen-free, non-halogenated and halogen-free, etc.) can lead to aconductive additive having a high electrical and thermal conductivity.Pre-lithiated pristine graphene and pre-sodiated pristine graphene werealso used as an anode active material for a lithium-ion battery and asodium-ion battery, respectively. Pristine graphene sheets were producedby using the direct ultrasonication or liquid-phase production process.

In a typical procedure, five grams of graphite flakes, ground toapproximately 20 μm or less in sizes, were dispersed in 1,000 mL ofdeionized water (containing 0.1% by weight of a dispersing agent, Zonyl®FSO from DuPont) to obtain a suspension. An ultrasonic energy level of85 W (Branson 5450 Ultrasonicator) was used for exfoliation, separation,and size reduction of graphene sheets for a period of 15 minutes to 2hours. The resulting graphene sheets are pristine graphene that havenever been oxidized and are oxygen-free and relatively defect-free.Pristine graphene is essentially free from any non-carbon elements.

Pristine graphene sheets, as a conductive additive, along with an anodeactive material (or cathode active material in the cathode) were thenincorporated in a battery using both the presently invented procedureand conventional procedure of slurry coating, drying and layerlaminating. Both lithium-ion batteries and lithium metal batteries(impregnation into cathode only) were investigated. Sodium-ion cellswere also studied.

EXAMPLE 6 Preparation of Prelithiated and Pre-Sodiated Graphene FluorideSheets as an Anode Active Material of a Lithium-Ion Battery orSodium-Ion Battery

Several processes have been used by us to produce GF, but only oneprocess is herein described as an example. In a typical procedure,highly exfoliated graphite (HEG) was prepared from intercalated compoundC₂F.xClF₃. HEG was further fluorinated by vapors of chlorine trifluorideto yield fluorinated highly exfoliated graphite (FHEG). Pre-cooledTeflon reactor was filled with 20-30 mL of liquid pre-cooled ClF₃, thereactor was closed and cooled to liquid nitrogen temperature. Then, nomore than 1 g of HEG was put in a container with holes for ClF₃ gas toaccess and situated inside the reactor. In 7-10 days a gray-beigeproduct with approximate formula C₂F was formed.

Subsequently, a small amount of FHEG (approximately 0.5 mg) was mixedwith 20-30 mL of an organic solvent (methanol and ethanol, separately)and subjected to an ultrasound treatment (280 W) for 30 min, leading tothe formation of homogeneous yellowish dispersions. Upon removal ofsolvent, the dispersion became a brownish powder. The graphene fluoridepowder was mixed with surface-stabilized lithium powder and in a liquidelectrolyte, allowing for pre-lithiation to occur before or afterimpregnating into pores of an anode current collector. Pre-sodiation ofgraphene fluoride was conducted electrochemically using a proceduresubstantially similar to a plating procedure.

EXAMPLE 7 Lithium Iron Phosphate (LFP) Cathode of a Lithium MetalBattery

LFP powder, un-coated or carbon-coated, is commercially available fromseveral sources. A LFP target for sputtering was prepared by compactingand sintering LFP powders together. Sputtering of LFP was conducted on agraphene film and, separately, carbon nano-fiber (CNF) mat. TheLFP-coated graphene film was then broken and pulverized to formLFP-coated graphene sheets.

Both carbon-coated LFP powder and graphene-supported LFP, separately,along with a liquid electrolyte, were then incorporated in a batteryusing both the presently invented procedure of impregnating andlaminating alkali metal-ion battery structures and the conventionalprocedure of slurry coating, drying and layer laminating.

EXAMPLE 8 Preparation of Disodium Terephthalate (Na₂C₈H₄O₄) as an AnodeActive Material of a Sodium-Ion Battery

Pure disodium terephthalate was obtained by the recrystallizationmethod. An aqueous solution was prepared via the addition ofterephthalic acid to an aqueous NaOH solution and then ethanol (EtOH)was added to the mixture to precipitate disodium terephthalate in awater/EtOH mixture. Because of resonance stabilization, terephtalic acidhas relatively low pKa values, which allow easy deprotonation by NaOH,affording disodium terephthalate (Na₂TP) through the acid-basechemistry. In a typical procedure, terephthalic acid (3.00 g, 18.06mmol) was treated with sodium hydroxide (1.517 g, 37.93 mmol) in EtOH(60 mL) at room temperature. After 24 h, the suspended reaction mixturewas centrifuged and the supernatant solution was decanted. Theprecipitate was re-dispersed in EtOH and then centrifuged again. Thisprocedure was repeated twice to yield a white solid. The product wasdried in vacuum at 150° C. for 1 h. In a separate sample, GO was addedto aqueous NaOH solution (5% by wt. of GO sheets) to prepare sheets ofgraphene-supported disodium terephthalate under comparable reactionconditions.

Both carbon-disodium terephthalate mixture powder and graphene-supporteddisodium terephthalate, separately, each along with a liquidelectrolyte, were then incorporated in a battery using both thepresently invented procedure of slurry impregnation into foam pores ofan anode current collector and the conventional procedure of slurrycoating, drying and layer laminating.

EXAMPLE 9 V₂O₅ as an Example of a Transition Metal Oxide Cathode ActiveMaterial of a Lithium Battery

V₂O₅ powder alone is commercially available. For the preparation of agraphene-supported V₂O₅ powder sample, in a typical experiment, vanadiumpentoxide gels were obtained by mixing V₂O₅ in a LiCl aqueous solution.The Li⁺-exchanged gels obtained by interaction with LiCl solution (theLi:V molar ratio was kept as 1:1) was mixed with a GO suspension andthen placed in a Teflon-lined stainless steel 35 ml autoclave, sealed,and heated up to 180° C. for 12 h. After such a hydrothermal treatment,the green solids were collected, thoroughly washed, ultrasonicated for 2minutes, and dried at 70° C. for 12 h followed by mixing with another0.1% GO in water, ultrasonicating to break down nano-belt sizes, andthen spray-drying at 200° C. to obtain graphene-embraced compositeparticulates.

Both V₂O₅ powder (with a carbon black powder as a conductive additive)and graphene-supported V₂O₅ powder, separately, along with a liquidelectrolyte, were then incorporated in a battery using both thepresently invented process and the conventional procedure of slurrycoating, drying and layer laminating.

EXAMPLE 10 LiCoO₂ as an Example of Lithium Transition Metal OxideCathode Active Material for a Lithium-Ion Battery

Commercially available LiCoO₂ powder and carbon black powder weredispersed in a liquid electrolyte to form cathode active materialmixtures, which were impregnated into Ni foam-based cathode currentcollector layers to form a cathode electrode. Graphite particle-liquidelectrolyte (i.e. the anode active mixture) was impregnated into poresof Cu foam layers to form anode electrodes. Additionally, a mixture ofgraphene embraced Si nano particles and liquid electrolyte wasimpregnated into pores of Cu foam to obtain an anode electrode. An anodeelectrode, a porous separator layer, and a cathode electrode wereassembled, compacted, and encased in a plastic-Al envelop to form abattery cell. The cell was then hermetically sealed.

On a separate basis, LiCoO₂ powder, carbon black powder, and PVDF resinbinder were dispersed in NMP solvent to form a slurry, which was coatedonto both sides of a AL foil current collector and then dried undervacuum to form a cathode layer. Graphite particles and PVDF resin binderwere dispersed in NMP solvent to form a slurry, which was coated ontoboth sides of a Cu foil current collector and then dried under vacuum toform an anode layer. The anode layer, separator, cathode layer were thenlaminated and encased in an Al-plastic housing, which was injected witha liquid electrolyte to form a conventional lithium-ion battery.

EXAMPLE 11 Cathode Active Materials Based on Mixed Transition MetalOxides

As examples, for the synthesis ofNa_(1.0)Li_(0.2)Ni_(0.25)Mn_(0.75)O_(δ), Ni_(0.25)Mn_(0.75)CO₃, orNi_(0.25)Mn_(0.75)(OH)₂ cathode active material, Na₂CO₃, and Li₂CO₃ wereused as starting compounds. Materials in appropriate mole ratios wereground together and heat-treated; first at 500° C. for 8 h in air, thenfinally at 800° C. for 8 h in air, and furnace cooled.

For electrode preparation using a conventional procedure, a sheet ofaluminum foil was coated with N-methylpyrrolidinone (NMP) slurry of thecathode mixture. The electrode mixture is composed of 82 wt % activeoxide material, 8 wt % conductive carbon black (Timcal Super-P), and 10wt. % PVDF binder (Kynar). After casting, the electrode was initiallydried at 70° C. for 2 h, followed by dynamic vacuum drying at 80° C. forat least 6 h. The sodium metal foil was cut from sodium chunks (Aldrich,99%) that were cleaned of any oil using hexanes, then rolled and punchedout. For the preparation of the presently invented slurry, NMP wasreplaced by a liquid electrolyte (propylene carbonate with 1 M ofNaClO₄). Such a slurry was directly impregnated into the pores of acathode current collector.

Both Na_(1.0)Li_(0.2)Ni_(0.25)Mn_(0.75)O_(δ) powder (with a carbon blackpowder as a conductive additive) and graphene-supportedNa_(1.0)Li_(0.2)Ni_(0.25)Mn_(0.75)O_(δ) powder, separately, along with aliquid electrolyte, were then incorporated in a battery using both thepresently invented procedure and the conventional procedure of slurrycoating, drying and layer laminating.

The electrolyte was propylene carbonate with 1 M of NaClO₄ electrolytesalt (Aldrich, 99%). Pouch cells were galvanostatically cycled to acutoff of 4.2 V vs. Na/Na⁺ (15 mA/g) and then discharged at variouscurrent rates to a cutoff voltage of 2.0 V.

In all battery cells prepared, charge storage capacities were measuredperiodically and recorded as a function of the number of cycles. Thespecific discharge capacity herein referred to is the total chargeinserted into the cathode during the discharge, per unit mass of thecomposite cathode (counting the weights of cathode active material,conductive additive or support, binder, and any optional additivecombined, but excluding the current collector). The specific chargecapacity refers to the amount of charges per unit mass of the compositecathode. The specific energy and specific power values presented in thissection are based on the total cell weight for all pouch cells. Themorphological or micro-structural changes of selected samples after adesired number of repeated charging and recharging cycles were observedusing both transmission electron microscopy (TEM) and scanning electronmicroscopy (SEM).

EXAMPLE 12 Na₃V₂(PO₄)₃/C and Na₃V₂(PO₄)₃/Graphene Cathodes

The Na₃V₂(PO₄)₃/C sample was synthesized by a solid state reactionaccording to the following procedure: a stoichiometric mixture ofNaH₂PO₄.2H₂O (99.9%, Alpha) and V₂O₃ (99.9%, Alpha) powders was put inan agate jar as a precursor and then the precursor was ball-milled in aplanetary ball mill at 400 rpm in a stainless steel vessel for 8 h.During ball milling, for the carbon coated sample, sugar (99.9%, Alpha)was also added as the carbon precursor and the reductive agent, whichprevents the oxidation of V³⁺. After ball milling, the mixture waspressed into a pellet and then heated at 900° C. for 24 h in Aratmosphere. Separately, the Na₃V₂(PO₄)₃/Graphene cathode was prepared ina similar manner, but with sugar replaced by graphene oxide.

The cathode active materials were used in several Na metal cellscontaining 1 M of NaPF₆ salt in PC+DOL as the electrolyte. Bothconventional NMP slurry coating process and the invented directelectrolyte impregnation into the pores of a conductive porous layer(current collector) were followed to produce Na metal cells.

EXAMPLE 13 Organic Material (Li₂C₆O₆) as a Cathode Active Material of aLithium Metal Battery

In order to synthesize dilithium rhodizonate (Li₂C₆O₆), the rhodizonicacid dihydrate (species 1 in the following scheme) was used as aprecursor. A basic lithium salt, Li₂CO₃ can be used in aqueous media toneutralize both enediolic acid functions. Strictly stoichiometricquantities of both reactants, rhodizonic acid and lithium carbonate,were allowed to react for 10 hours to achieve a yield of 90%. Dilithiumrhodizonate (species 2) was readily soluble even in a small amount ofwater, implying that water molecules are present in species 2. Water wasremoved in a vacuum at 180° C. for 3 hours to obtain the anhydrousversion (species 3).

A mixture of a cathode active material (Li₂C₆O₆) and a conductiveadditive (carbon black, 15%) was ball-milled for 10 minutes and theresulting blend was grinded to produce composite particles. Theelectrolyte was 1M of lithium hexafluorophosphate (LiPF₆) in PC-EC.

It may be noted that the two Li atoms in the formula Li₂C₆O₆ are part ofthe fixed structure and they do not participate in reversible lithiumion storing and releasing. This implies that lithium ions must come fromthe anode side. Hence, there must be a lithium source (e.g. lithiummetal or lithium metal alloy) at the anode. As illustrated in FIG. 1(E),the anode current collector (Cu foil) is deposited with a layer oflithium (e.g. via sputtering or electrochemical plating). This can bedone prior to assembling the lithium-coated layer (or simply a lithiumfoil), a porous separator, and an impregnated cathode layer into acasing envelop. Under a compression force, the pores of the conductiveporous layers are infiltrated with the cathode active material andconductive additive (Li₂C₆O₆/C composite particles) wetted with theliquid electrolyte. For comparison, the corresponding conventional Limetal cell was also fabricated by the conventional procedures of slurrycoating, drying, laminating, packaging, and electrolyte injection.

EXAMPLE 14 Organic Material (Na₂C₆O₆) as a Cathode Active Material of aSodium Metal Battery

In order to synthesize disodium rhodizonate (Na₂C₆O₆), the rhodizonicacid dihydrate (species 1 in the following scheme) was used as aprecursor. A basic sodium salt, Na₂CO₃ can be used in aqueous media toneutralize both enediolic acid functions. Strictly stoichiometricquantities of both reactants, rhodizonic acid and sodium carbonate, wereallowed to react for 10 hours to achieve a yield of 80%. Disodiumrhodizonate (species 2) was readily soluble even in a small amount ofwater, implying that water molecules are present in species 2. Water wasremoved in a vacuum at 180° C. for 3 hours to obtain the anhydrousversion (species 3).

A mixture of a cathode active material (Na₂C₆O₆) and a conductiveadditive (carbon black, 15%) was ball-milled for 10 minutes and theresulting blend was grinded to produce composite particles. Theelectrolyte was 1M of sodium hexafluorophosphate (NaPF₆) in PC-EC.

The two Na atoms in the formula Na₂C₆O₆ are part of the fixed structureand they do not participate in reversible lithium ion storing andreleasing. The sodium ions must come from the anode side. Hence, theremust be a sodium source (e.g. sodium metal or sodium metal alloy) at theanode. As illustrated in FIG. 1(E), the anode current collector (Cufoil) is deposited with a layer of sodium (e.g. via sputtering orelectrochemical plating). This can be done prior to assembling thesodium-coated layer or simply a sodium foil, a porous separator, and afoamed cathode current collector into a dry cell. The pores of thecathode current collector are them infiltrated with the suspension ofcathode active material and conductive additive (Na₂C₆O₆/C compositeparticles) dispersed in the liquid electrolyte. For comparison, thecorresponding conventional Na metal cell was also fabricated by theconventional procedures of slurry coating, drying, laminating,packaging, and electrolyte injection.

EXAMPLE 15 Metal Naphthalocyanine-RGO Hybrid Cathode of a Lithium MetalBattery

CuPc-coated graphene sheets were obtained by vaporizing CuPc in achamber along with a graphene film (5 nm) prepared from spin coating ofRGO-water suspension. The resulting coated film was cut and milled toproduce CuPc-coated graphene sheets, which were used as a cathode activematerial in a lithium metal battery. This battery has a lithium metalfoil as the anode active material and 1-3.6 M of LiClO₄ in propylenecarbonate (PC) solution as the electrolyte.

EXAMPLE 16 Preparation of MoS₂/RGO Hybrid Material as a Cathode ActiveMaterial of a Lithium Metal Battery

A wide variety of inorganic materials were investigated in this example.For instance, an ultra-thin MoS₂/RGO hybrid was synthesized by aone-step solvothermal reaction of (NH₄)₂MoS₄ and hydrazine in anN,N-dimethylformamide (DMF) solution of oxidized graphene oxide (GO) at200° C. In a typical procedure, 22 mg of (NH₄)₂MoS₄ was added to 10 mgof GO dispersed in 10 ml of DMF. The mixture was sonicated at roomtemperature for approximately 10 min until a clear and homogeneoussolution was obtained. After that, 0.1 ml of N₂H₄.H₂O was added. Thereaction solution was further sonicated for 30 min before beingtransferred to a 40 mL Teflon-lined autoclave. The system was heated inan oven at 200° C. for 10 h. Product was collected by centrifugation at8000 rpm for 5 min, washed with DI water and recollected bycentrifugation. The washing step was repeated for at least 5 times toensure that most DMF was removed. Finally, product was dried, mixed withliquid electrolyte to produce active cathode mixture slurry forimpregnation.

EXAMPLE 17 Preparation of Two-Dimensional (2D) Layered Bi₂Se₃Chalcogenide Nanoribbons

The preparation of (2D) layered Bi₂Se₃ chalcogenide nanoribbons iswell-known in the art. For instance, Bi₂Se₃ nanoribbons were grown usingthe vapor-liquid-solid (VLS) method. Nanoribbons herein produced are, onaverage, 30-55 nm thick with widths and lengths ranging from hundreds ofnanometers to several micrometers. Larger nanoribbons were subjected toball-milling for reducing the lateral dimensions (length and width) tobelow 200 nm. Nanoribbons prepared by these procedures (with or withoutthe presence of graphene sheets or exfoliated graphite flakes) were usedas a cathode active material of a lithium metal battery.

EXAMPLE 18 MXenes Powder+Chemically Activated RGO

Selected MXenes, were produced by partially etching out certain elementsfrom layered structures of metal carbides such as Ti₃AlC₂. For instance,an aqueous 1 M NH₄HF₂ was used at room temperature as the etchant forTi₃AlC₂. Typically, MXene surfaces are terminated by O, OH, and/or Fgroups, which is why they are usually referred to as M_(n+1)X_(n)T_(x),where M is an early transition metal, X is C and/or N, T representsterminating groups (O, OH, and/or F), n=1, 2, or 3, and x is the numberof terminating groups. The MXene materials investigated includeTi₂CT_(x), Nb₂CT_(x), V₂CT_(x), Ti₃CNT_(x), and Ta₄C₃T_(x). Typically,35-95% MXene and 5-65% graphene sheets were mixed in a liquidelectrolyte to form cathode active material mixture slurry.

EXAMPLE 19 Preparation of Graphene-Supported MnO₂ Cathode ActiveMaterial

The MnO₂ powder was synthesized by two methods (each with or without thepresence of graphene sheets). In one method, a 0.1 mol/L KMnO₄ aqueoussolution was prepared by dissolving potassium permanganate in deionizedwater. Meanwhile 13.32 g surfactant of high purity sodiumbis(2-ethylhexyl) sulfosuccinate was added in 300 mL iso-octane (oil)and stirred well to get an optically transparent solution. Then, 32.4 mLof 0.1 mol/L KMnO₄ solution and selected amounts of GO solution wereadded in the solution, which was ultrasonicated for 30 min to prepare adark brown precipitate. The product was separated, washed several timeswith distilled water and ethanol, and dried at 80° C. for 12 h. Thesample is graphene-supported MnO₂ in a powder form, which was mixed in aliquid electrolyte to form cathode active material mixture slurry.

EXAMPLE 20 Graphene-Enhanced Nano Silicon Fabricated from TEOS as anAnode Active Material of a Lithium-Ion Battery

Dilute 1 wt. % N002-PS to 0.2 wt. % N002-PS by DI water, and place thediluted PS solution to the ultrasonic bath and ultrasonic process for 30minutes. Gradually add TEOS (0.2 wt. % N002-PS:TEOS=5:2) while stirringthe PS solution. Then, keep stirring for 24 hours to get a completehydrolysis of TEOS. Dropwise add 10% NH₃.H₂O till the formation of gel,and the gel can be called as TP gel. Grind the TP gel to tiny particles.Oven dries at 120° C. for 2 hours, at 150° C. for 4 hours. Mix the driedTP particles with Mg in a ratio of 10:7. Use 20 times amount of 7 mm SSballs and ball mill under Argon protection, gradually increase therotating speed to 250 rpm. Put certain amount of TPM powders in Nickelcrucible and heat treatment at 680° C. Prepare certain amount of 2M HClsolution. Then gradually add heat treated TPM powders to the acidsolution. Keep the reaction for 2-24 hours, and then put the turbidliquid to the ultrasonic bath and ultrasonic process for 1 hour. Pourout the suspension to the filtration system. Discard the bottom largeparticles. Use DI water to rinse three times. Dry the yellow paste andblend the yellow paste to powders. The as-prepared nano particle has aSSA value range of 30 m²/g to 200 m²/g due to different ratio ofgraphene contents

A certain amount of the dried TPM particles is then put into mufflefurnace and calcined at 400° C.-600° C. for 2 hours under air purging toremove the carbon content from the nanocomposite, producinggraphene-free yellow-color silicon nano powders. Both Si nano powder andgraphene-wrapped Si nano particles were used as a high-capacity anodeactive material.

EXAMPLE 21 Cobalt Oxide (Co₃O₄) Particulates as an Anode Active Material

Although LiCoO₂ is a cathode active material, Co₃O₄ is an anode activematerial of a lithium-ion battery since LiCoO₂ is at an electrochemicalpotential of approximately +4.0 volts relative to Li/Li⁺ and Co₃O₄ is atan electrochemical potential of approximately +0.8 volts relative toLi/Li⁺.

An appropriate amount of inorganic salts Co(NO₃)₂.6H₂O and,subsequently, ammonia solution (NH₃.H₂O, 25 wt %) were slowly added intoa GO suspension. The resulting precursor suspension was stirred forseveral hours under an argon flow to ensure a complete reaction. Theobtained Co(OH)₂/graphene precursor suspension was divided into twoportions. One portion was filtered and dried under vacuum at 70° C. toobtain a Co(OH)₂/graphene composite precursor. This precursor wascalcined at 450° C. in air for 2 h to form the layered Co₃O₄/graphenecomposites, which are characterized by having Co₃O₄-coated graphenesheets overlapping one another. These Co₃O₄-coated graphene sheets areanother high-capacity anode active material.

EXAMPLE 22 Graphene-Enhanced Tin Oxide Particulates as an Anode ActiveMaterial

Tin oxide (SnO₂) nano particles, an anode active material, were obtainedby the controlled hydrolysis of SnCl₄.5H₂O with NaOH using the followingprocedure: SnCl₄.5H₂O (0.95 g, 2.7 m-mol) and NaOH (0.212 g, 5.3 m-mol)were dissolved in 50 mL of distilled water each. The NaOH solution wasadded drop-wise under vigorous stirring to the tin chloride solution ata rate of 1 mL/min. This solution was homogenized by sonication for 5min. Subsequently, the resulting hydrosol was reacted with the GOdispersion for 3 hours. To this mixed solution, few drops of 0.1 M ofH₂SO₄ were added to flocculate the product. The precipitated solid wascollected by centrifugation, washed with water and ethanol, and dried invacuum. The dried product was heat-treated at 400° C. for 2 h under Aratmosphere.

EXAMPLE 23 Preparation of Graphene-Supported MnO₂ and NaMnO₂ CathodeActive Material

The MnO₂ powder was synthesized by two methods (each with or without thepresence of graphene sheets). In one method, a 0.1 mol/L KMnO₄ aqueoussolution was prepared by dissolving potassium permanganate in deionizedwater. Meanwhile 13.32 g surfactant of high purity sodiumbis(2-ethylhexyl) sulfosuccinate was added in 300 mL iso-octane (oil)and stirred well to get an optically transparent solution. Then, 32.4 mLof 0.1 mol/L KMnO₄ solution and selected amounts of GO solution wereadded in the solution, which was ultrasonicated for 30 min to prepare adark brown precipitate. The product was separated, washed several timeswith distilled water and ethanol, and dried at 80° C. for 12 h. Thesample is graphene-supported MnO₂ in a powder form, which was dispersedin a liquid electrolyte to form a slurry and impregnated into pores of afoamed current collector.

Additionally, NaMnO₂ and NaMnO₂/graphene composite were synthesized byball-milling mixtures of Na₂CO₃ and MnO₂ (at a molar ratio of 1:2), withor without graphene sheets, for 12 h followed by heating at 870° C. for10 h.

EXAMPLE 24 Preparation of Electrodes for Potassium Metal Cells

A sheet of potassium-coated graphene film was used as the anode activematerial while a layer of PVDF-bonded reduced graphene oxide (RGO)sheets, supplied from Angstron Materials, Inc. (Dayton, Ohio), was usedas the cathode active material. The electrolyte used was 1 M of KClO₄salt dissolved in a mixture of propylene carbonate and DOL (1/1 ratio).Charge-discharge curves were obtained at several current densities (from50 mA/g to 50 A/g), corresponding to different C rates, with theresulting energy density and power density data measured and calculated.

EXAMPLE 25 Preparation and Electrochemical Testing of Various AlkaliMetal Battery Cells

For most of the anode and cathode active materials investigated, weprepared alkali metal-ion cells or alkali metal cells using both thepresently invented method and the conventional method.

With the conventional method, a typical anode composition includes 85wt. % active material (e.g., Si- or Co₃O₄-coated graphene sheets), 7 wt.% acetylene black (Super-P), and 8 wt. % polyvinylidene fluoride binder(PVDF, 5 wt. % solid content) dissolved in N-methyl-2-pyrrolidinoe(NMP). After coating the slurries on Cu foil, the electrodes were driedat 120° C. in vacuum for 2 h to remove the solvent. With the instantmethod, typically no binder resin is needed or used, saving 8% weight(reduced amount of non-active materials). Cathode layers are made in asimilar manner (using Al foil as the cathode current collector) usingthe conventional slurry coating and drying procedures. An anode layer,separator layer (e.g. Celgard 2400 membrane), and a cathode layer arethen laminated together and housed in a plastic-Al envelop. The cell isthen injected with 1 M LiPF₆ electrolyte solution dissolved in a mixtureof ethylene carbonate (EC) and diethyl carbonate (DEC) (EC-DEC, 1:1v/v). In some cells, ionic liquids were used as the liquid electrolyte.The cell assemblies were made in an argon-filled glove-box.

In some examples of the presently invented process, we assembledtypically 1-5 layers of pre-impregnated conductive porous structures(e.g. Cu foam) to form an anode electrode. Separately, we assembledtypically 1-5 conductive porous layers (e.g. Al or graphite foam)pre-impregnated with a cathode active material mixture to form a cathodeelectrode. An anode electrode, a porous separator layer, and a cathodeelectrode were then laminated to form a battery assembly.

The cyclic voltarnmetry (CV) measurements were carried out using anArbin electrochemical workstation at a typical scanning rate of 1 mV/s.In addition, the electrochemical performances of various cells were alsoevaluated by galvanostatic charge/discharge cycling at a current densityof from 50 mA/g to 10 A/g. For long-term cycling tests, multi-channelbattery testers manufactured by LAND were used.

In lithium-ion battery industry, it is a common practice to define thecycle life of a battery as the number of charge-discharge cycles thatthe battery suffers 20% decay in capacity based on the initial capacitymeasured after the required electrochemical formation.

EXAMPLE 26 Representative Testing Results for Lithium Cells

For each sample, several current densities (representingcharge/discharge rates) were imposed to determine the electrochemicalresponses, allowing for calculations of energy density and power densityvalues required of the construction of a Ragone plot (power density vs.energy density). Shown in FIG. 5 are Ragone plots (gravimetric andvolumetric power density vs. energy density) of lithium-ion batterycells containing graphite particles as the anode active material andcarbon-coated LFP particles as the cathode active materials. Two of the4 data curves are for the cells prepared according to an embodiment ofinstant invention and the other two by the conventional slurry coatingof electrodes (roll-coating). Several significant observations can bemade from these data:

Both the gravimetric and volumetric energy densities and power densitiesof the lithium-ion battery cells prepared by the presently inventedmethod (denoted as “inventive” in the figure legend) are significantlyhigher than those of their counterparts prepared via the conventionalroll-coating method (denoted as “conventional”). A change from an anodethickness of 160 μm (coated on a flat solid Cu foil) to a thickness of215 μm (all accommodated in pores of a Ni foam having 85% porosity) anda corresponding change in the cathode to maintain a balanced capacityratio results in a gravimetric energy density increase from 165 Wh/kg to264 Wh/kg. Even more surprisingly, the volumetric energy density isincreased from 412.5 Wh/L to 739 Wh/L. This latter value of 739 Wh/L hasnever been previously achieved with a lithium-ion battery using agraphite anode and a lithium iron phosphate cathode.

These huge differences cannot be simply ascribed to the increases in theelectrode thickness and the mass loading alone. The differences arelikely due to the significantly higher active material mass loading (notjust mass loading) associated with the presently invented cells, reducedproportion of overhead (non-active) components relative to the activematerial weight/volume, no need to have a binder resin, surprisinglybetter utilization of the electrode active material (most, if not all,of the graphite particles and LFP particles contributing to the lithiumion storage capacity; no dry pockets or ineffective spots in theelectrode, particularly under high charge/discharge rate conditions),and the surprising ability of the inventive method to more effectivelypack active material particles in the pores of the porous conductivelayer (foamed current collector). These have not been taught, suggested,or even slightly hinted in the art of lithium-ion battery. Furthermore,the maximum power density is increased from 621 W/kg to 1245 W/kg. Thismight have been due to significantly reduced internal resistance againstelectron transport and lithium ion transport.

FIG. 6 shows the Ragone plots (both gravimetric and volumetric powerdensity vs. gravimetric and volumetric energy density) of two cells,both containing graphene-embraced Si nano particles as the anode activematerial and LiCoO₂ nano particles as the cathode active material. Theexperimental data were obtained from the Li-ion battery cells that wereprepared by the presently invented method and those by the conventionalslurry coating of electrodes.

These data indicate that both the gravimetric and volumetric energydensities and power densities of the battery cells prepared by thepresently invented method are significantly higher than those of theircounterparts prepared via the conventional method. Again, thedifferences are huge. The conventionally made cells exhibit agravimetric energy density of 265 Wh/kg and volumetric energy density of689 Wh/L, but the presently invented cells deliver 422 Wh/kg and 1,221Wh/L, respectively. The cell-level energy density of 1,223 Wh/L hasnever been previously achieved with any rechargeable lithium battery.The power densities as high as 2422 W/kg and 7,024 W/L are alsounprecedented for lithium-ion batteries. The power densities of thecells prepared via the presently invented process are alwayssignificantly higher than those of the corresponding cells prepared byconventional processes.

These energy density and power density differences are mainly due to thehigh active material mass loading (>25 mg/cm² in the anode and >45mg/cm² in the cathode) associated with the presently invented cells,reduced proportion of overhead (non-active) components relative to theactive material weight/volume, no need to have a binder resin, theability of the inventive method to better utilize the active materialparticles (all particles being accessible to liquid electrolyte and fastion and electron kinetics), and to more effectively pack active materialparticles in the pores of the foamed current collectors.

Shown in FIG. 7 are Ragone plots of lithium metal batteries containing alithium foil as the anode active material, dilithium rhodizonate(Li₂C₆O₆) as the cathode active material, and lithium salt(LiPF₆)-PC/DEC as organic liquid electrolyte. The data are for bothlithium metal cells prepared by the presently invented method and thoseby the conventional slurry coating of electrodes. These data indicatethat both the gravimetric and volumetric energy densities and powerdensities of the lithium metal cells prepared by the presently inventedmethod are significantly higher than those of their counterpartsprepared via the conventional method. Again, the differences are hugeand are likely due to the significantly higher active material massloading (not just mass loading) associated with the presently inventedcells, reduced proportion of overhead (non-active) components relativeto the active material weight/volume, no need to have a binder resin,surprisingly better utilization of the electrode active material (most,if not all, of the active material contributing to the lithium ionstorage capacity; no dry pockets or ineffective spots in the electrode,particularly under high charge/discharge rate conditions), and thesurprising ability of the inventive method to more effectively packactive material particles in the pores of the foamed current collector.

Quite noteworthy and unexpected is the observation that the gravimetricenergy density of the presently invented lithium metal-organic cathodecell is as high as 520 Wh/kg, higher than those of all rechargeablelithium-metal or lithium-ion batteries ever reported (recall thatcurrent Li-ion batteries store 150-220 Wh/kg based on the total cellweight). Also quite astonishing is the observation that the volumetricenergy density of such an organic cathode-based battery is as high as1040 Wh/L, an unprecedentedly high value that tops those of alllithium-ion and lithium metal batteries ever reported. Furthermore, fororganic cathode active material-based lithium batteries, a gravimetricpower density of 1,752 W/kg and maximum volumetric power density of5,080 W/L would have been un-thinkable.

It is of significance to point out that reporting the energy and powerdensities per weight of active material alone on a Ragone plot, as didby many researchers, may not give a realistic picture of the performanceof the assembled supercapacitor cell. The weights of other devicecomponents also must be taken into account. These overhead components,including current collectors, electrolyte, separator, binder,connectors, and packaging, are non-active materials and do notcontribute to the charge storage amounts. They only add weights andvolumes to the device. Hence, it is desirable to reduce the relativeproportion of overhead component weights and increase the activematerial proportion. However, it has not been possible to achieve thisobjective using conventional battery production processes. The presentinvention overcomes this long-standing, most serious problem in the artof lithium batteries.

In commercial lithium-ion batteries having an electrode thickness of100-200 μm, the weight proportion of the anode active material (e.g.graphite or carbon) in a lithium-ion battery is typically from 12% to17%, and that of the cathode active material (for inorganic material,such as LiMn₂O₄) from 22% to 41%, or from 10% to 15% for organic orpolymeric. Hence, a factor of 3 to 4 is frequently used to extrapolatethe energy or power densities of the device (cell) from the propertiesbased on the active material weight alone. In most of the scientificpapers, the properties reported are typically based on the activematerial weight alone and the electrodes are typically very thin (<<100μm, and mostly <<50 μm). The active material weight is typically from 5%to 10% of the total device weight, which implies that the actual cell(device) energy or power densities may be obtained by dividing thecorresponding active material weight-based values by a factor of 10 to20. After this factor is taken into account, the properties reported inthese papers do not really look any better than those of commercialbatteries. Thus, one must be very careful when it comes to read andinterpret the performance data of batteries reported in the scientificpapers and patent applications.

EXAMPLE 27 Achievable Electrode Thickness and its Effect onElectrochemical Performance of Lithium Battery Cells

One might be tempted to think the electrode thickness of a lithiumbattery is a design parameter that can be freely adjusted foroptimization of device performance. Contrary to this perception, inreality, the lithium battery electrode thickness ismanufacturing-limited and one cannot produce electrodes of goodstructural integrity that exceed certain thickness level in a realindustrial manufacturing environment (e.g. a roll-to-roll coatingfacility). The conventional battery electrode design is based on coatingan electrode layer on a flat metal current collector, which has severalmajor problems: (a) A thick coating on solid Cu foil or Al foil requiresa long drying time (requiring a heating zone that is 30-100 meterslong). (b) Thick electrodes tend to get delaminated or cracked upondrying and subsequent handling, and even with a resin binder proportionas high as 15-20% to hopefully improve the electrode integrity thisproblem remains a major limiting factor. Thus, such an industry practiceof roll-coating of slurry on a solid flat current collector does notallow for high active material mass loadings. (c) A thick electrodeprepared by coating, drying, and compression makes it difficult forelectrolyte (injected into a cell after the cell is made) to permeatethrough the electrode and, as such, a thick electrode would mean manydry pockets or spots that are not wetted by the electrolyte. This wouldimply a poor utilization of the active materials. The instant inventionsolves these long-standing, critically important issues associated withlithium batteries.

Shown in FIG. 8 are the cell-level gravimetric (Wh/kg) and volumetricenergy densities (Wh/L) of lithium metal cells plotted over theachievable cathode thickness range of the MnO₂/RGO cathode prepared viathe conventional method without delamination and cracking and those bythe presently invented method. In this figure, the data points arelabelled as the gravimetric (♦) and volumetric (▴) energy density of theconventional Li—MnO₂/RGO batteries and the gravimetric (▪) andvolumetric (x) energy density of the presently invented ones.

The electrodes can be fabricated up to a thickness of 100-200 μm usingthe conventional slurry coating process. However, in contrast, there isno theoretical limit on the electrode thickness that can be achievedwith the presently invented method. Typically, the practical electrodethickness is from 10 μm to 1000 μm, more typically from 100 μm to 800μm, and most typically from 200 μm to 600 μm.

These data further confirm the surprising effectiveness of the presentlyinvented method in producing ultra-thick lithium battery electrodes notpreviously achievable. These ultra-thick electrodes in lithium metalbatteries lead to exceptionally high cathode active material massloading, typically significantly >25 mg/cm² (more typically >30 mg/cm²,further typically >40 mg/cm², often >50 mg/cm², and even >60 mg/cm²) foran inorganic cathode active material. These high active material massloadings have not been possible to obtain with conventional lithiumbatteries made by the slurry coating processes. These high activematerial mass loadings led to exceptionally high gravimetric andvolumetric energy densities that otherwise have not been previouslyachieved (e.g. 514 Wh/kg and 1054 Wh/L of the presently invented lithiummetal battery) given the same battery system.

EXAMPLE 28 Achievable Active Material Weight Percentage in a Cell andits Effect on Electrochemical Performance of Lithium Battery Cells

Because the weight of the anode and cathode active materials combinedaccounts for up to about 30%-50% of the total mass of the packagedcommercial lithium batteries, a factor of 30%-50% must be used toextrapolate the energy or power densities of the device from theperformance data of the active materials alone. Thus, the energy densityof 500 Wh/kg of combined graphite and NMC (lithium nickel manganesecobalt oxide) weights will translate to about 150-250 Wh/kg of thepackaged cell. However, this extrapolation is only valid for electrodeswith thicknesses and densities similar to those of commercial electrodes(150 μm or about 15 mg/cm² of the graphite anode and 30 mg/cm² of NMCcathode). An electrode of the same active material that is thinner orlighter will mean an even lower energy or power density based on thecell weight. Thus, it would be desirable to produce a lithium-ionbattery cell having a high active material proportion. Unfortunately, ithas not been previously possible to achieve a total active materialproportion greater than 45% by weight in most of the commerciallithium-ion batteries.

The presently invented method enables the lithium batteries to go wellbeyond these limits for all active materials investigated. As a matterof fact, the instant invention makes it possible to elevate the activematerial proportion above 90% if so desired; but typically from 45% to85%, more typically from 40% to 80%, even more typically from 40% to75%, and most typically from 50% to 70%.

Shown in FIG. 9 are the cell-level gravimetric and volumetric energydensities of the graphite/NMC cells prepared by the presently inventedmethod and the conventional roll-coating method. These data furtherdemonstrate the implications of our ability to take the total activematerial mass beyond 50%, enabling the attainment of unexpectedly highgravimetric and volumetric energy densities that have not beenpreviously possible given the same lithium battery system (e.g. elevatedfrom 190 Wh/kg to 360 Wh/kg and from 510 Wh/L to 970 Wh/L).

EXAMPLE 26 Representative Testing Results of Sodium Metal and PotassiumMetal Cells

Shown in FIG. 10 are Ragone plots (gravimetric and volumetric powerdensity vs. energy density) of Na-ion battery cells containing hardcarbon particles as the anode active material and carbon-coatedNa₃V₂(PO₄)₂F₃ particles as the cathode active materials. Two of the 4data curves are for the cells prepared according to an embodiment ofinstant invention and the other two by the conventional slurry coatingof electrodes (roll-coating). Several significant observations can bemade from these data:

Both the gravimetric and volumetric energy densities and power densitiesof the sodium-ion battery cells prepared by the presently inventedmethod (denoted as “inventive” in the figure legend) are significantlyhigher than those of their counterparts prepared via the conventionalroll-coating method (denoted as “conventional”). A change from an anodethickness of 150 μm (coated on a flat solid Cu foil) to a thickness of225 μm (all accommodated in pores of a Ni foam having 85% porosity) anda corresponding change in the cathode to maintain a balanced capacityratio results in a gravimetric energy density increase from 115 Wh/kg to154 Wh/kg. Even more surprisingly, the volumetric energy density isincreased from 241 Wh/L to 493 Wh/L. This latter value of 493 Wh/L isexceptional for a sodium-ion battery using a hard carbon anode and asodium transition metal phosphate-type cathode.

These huge differences cannot be simply ascribed to the increases in theelectrode thickness and the mass loading. The differences are likely dueto the significantly higher active material mass loading (relative toother materials) associated with the presently invented cells, reducedproportion of overhead (non-active) components relative to the activematerial weight/volume, no need to have a binder resin, surprisinglybetter utilization of the electrode active material (most, if not all,of the hard carbon particles and Na₃V₂(PO₄)₂F₃ particles contributing tothe sodium ion storage capacity; no dry pockets or ineffective spots inthe electrode, particularly under high charge/discharge rateconditions), and the surprising ability of the inventive method to moreeffectively pack active material particles in the pores of theconductive porous layers (foamed current collectors).

The presently invented sodium-ion cells also deliver significantlyhigher energy densities than those of conventional cells. This is alsounexpected.

FIG. 11 shows the Ragone plots (both gravimetric and volumetric powerdensity vs.

gravimetric and volumetric energy density) of two cells, both containinggraphene-embraced Sn nano particles as the anode active material andNaFePO₄ nano particles as the cathode active material. The experimentaldata were obtained from the Na-ion battery cells that were prepared bythe presently invented method and those by the conventional slurrycoating of electrodes.

These data indicate that both the gravimetric and volumetric energydensities and power densities of the sodium battery cells prepared bythe presently invented method are significantly higher than those oftheir counterparts prepared via the conventional method. Again, thedifferences are huge. The conventionally made cells exhibit agravimetric energy density of 185 Wh/kg and volumetric energy density of388 Wh/L, but the presently invented cells deliver 304 Wh/kg and 820Wh/L, respectively. The cell-level volumetric energy density of 820 Wh/Lhas never been previously achieved with any rechargeable sodiumbatteries. In fact, even the state-of-the-art lithium-ion battery rarelyexhibits a volumetric energy density higher than 750 Wh/L. The powerdensities as high as 1235 W/kg and 3,581 W/L are also unprecedented fortypically higher-energy lithium-ion batteries, let alone for sodium-ionbatteries.

These energy density and power density differences are mainly due to thehigh active material mass loading (>25 mg/cm² in the anode and >45mg/cm² in the cathode) associated with the presently invented cells,reduced proportion of overhead (non-active) components relative to theactive material weight/volume, no need to have a binder resin, theability of the inventive method to better utilize the active materialparticles (all particles being accessible to liquid electrolyte and fastion and electron kinetics), and to more effectively pack active materialparticles in the pores of the foamed current collectors.

Shown in FIG. 12 are Ragone plots of sodium metal batteries containing asodium foil as the anode active material, disodium rhodizonate (Na₂C₆O₆)as the cathode active material, and lithium salt (NaPF₆)-PC/DEC asorganic liquid electrolyte. The data are for both sodium metal cellsprepared by the presently invented method and those by the conventionalslurry coating of electrodes. These data indicate that both thegravimetric and volumetric energy densities and power densities of thesodium metal cells prepared by the presently invented method aresignificantly higher than those of their counterparts prepared via theconventional method. Again, the differences are huge and are likely dueto the significantly higher active material mass loading associated withthe presently invented cells, reduced proportion of overhead(non-active) components relative to the active material weight/volume,no need to have a binder resin, surprisingly better utilization of theelectrode active material (most, if not all, of the active materialcontributing to the sodium ion storage capacity; no dry pockets orineffective spots in the electrode, particularly under highcharge/discharge rate conditions), and the surprising ability of theinventive method to more effectively pack active material particles inthe pores of the foamed current collector.

Quite noteworthy and unexpected is the observation that the gravimetricenergy density of the presently invented sodium metal-organic cathodecell is as high as 322 Wh/kg, higher than those of all rechargeablesodium metal or sodium-ion batteries ever reported (recall that currentNa-ion batteries typically store 100-150 Wh/kg based on the total cellweight). Furthermore, for organic cathode active material-based sodiumbatteries (even for corresponding lithium batteries), a gravimetricpower density of 1,254 W/kg and volumetric power density of 3,636 W/Lwould have been un-thinkable.

It is of significance to point out that reporting the energy and powerdensities per weight of active material alone on a Ragone plot, as didby many researchers, may not give a realistic picture of the performanceof the assembled battery cell. The weights of other device componentsalso must be taken into account. These overhead components, includingcurrent collectors, electrolyte, separator, binder, connectors, andpackaging, are non-active materials and do not contribute to the chargestorage amounts. They only add weights and volumes to the device. Hence,it is desirable to reduce the relative proportion of overhead componentweights and increase the active material proportion. However, it has notbeen possible to achieve this objective using conventional batteryproduction processes. The present invention overcomes thislong-standing, most serious problem in the art of lithium batteries.

In commercial lithium-ion batteries having an electrode thickness of 150μm, the weight proportion of the anode active material (e.g. graphite orcarbon) in a lithium-ion battery is typically from 12% to 17%, and thatof the cathode active material (for inorganic material, such as LiMn₂O₄)from 22% to 41%, or from 10% to 15% for organic or polymeric. Thecorresponding weight fractions in Na-ion batteries are expected to bevery similar since both the anode active materials and cathode activematerials have similar physical densities between two types of batteriesand the ratio of cathode specific capacity to the anode specificcapacity is also similar. Hence, a factor of 3 to 4 may be used toextrapolate the energy or power densities of the sodium cell from theproperties based on the active material weight alone. In most of thescientific papers, the properties reported are typically based on theactive material weight alone and the electrodes are typically very thin(<<100 μm and mostly <<50 μm). The active material weight is typicallyfrom 5% to 10% of the total device weight, which implies that the actualcell (device) energy or power densities may be obtained by dividing thecorresponding active material weight-based values by a factor of 10 to20. After this factor is taken into account, the properties reported inthese papers do not really look any better than those of commercialbatteries. Thus, one must be very careful when it comes to read andinterpret the performance data of batteries reported in the scientificpapers and patent applications.

The Ragone plot of a series of K-ion cells prepared by the conventionalslurry coating process and the Ragone plot of corresponding K-ion cellsprepared by the presently invented process are summarized and contrastedin FIG. 13. These data again confirm that the presently invented processworks well for making both Na and K metal batteries having ultra-highenergy densities and power densities.

We claim:
 1. A process for producing an alkali metal battery whereinsaid alkali metal is selected from Li, Na, K, or a combination thereof;said process comprising: (A) Continuously feeding an electricallyconductive porous layer to a cathode material impregnation zone, whereinsaid conductive porous layer has two opposed porous surfaces andcontains interconnected electron-conducting pathways; (B) Impregnating awet cathode active material mixture into said electrically conductiveporous layer from at least one of said two porous surfaces to form acathode electrode, wherein said wet cathode active material mixturecontains a cathode active material and an optional conductive additivemixed with a first liquid electrolyte; (C) Continuously feeding anelectrically conductive porous layer to an anode material impregnationzone, wherein said conductive porous layer has two opposed poroussurfaces and contains interconnected electron-conducting pathways; (D)Impregnating a wet anode active material mixture into said electricallyconductive porous layer from at least one of said two porous surfaces toform an anode electrode, wherein said wet anode active material mixturecontains an anode active material and an optional conductive additivemixed with a second liquid electrolyte; and (E) Stacking said anodeelectrode, a porous separator, and said cathode electrode to form saidalkali metal battery, wherein said anode electrode and/or said cathodeelectrode has a thickness no less than 100 μm; said anode activematerial has a material mass loading no less than 20 mg/cm² in saidanode electrode; and/or said cathode active material has a material massloading no less than 15 mg/cm² for an organic or polymer material or noless than 30 mg/cm² for an inorganic and non-polymer material in saidcathode electrode.
 2. The process of claim 1, wherein step (A) and step(B) include delivering, continuously or intermittently on demand, saidwet cathode active material mixture to said at least one porous surfacethrough spraying, printing, coating, casting, conveyor film delivery,and/or roller surface delivery; and/or wherein step (C) and step (D)include delivering, continuously or intermittently on demand, said wetanode active material mixture to said at least one porous surfacethrough spraying, printing, coating, casting, conveyor film delivery,and/or roller surface delivery.
 3. A process for producing an alkalimetal battery wherein said alkali metal is selected from Li, Na, K, or acombination thereof; said process comprising: (A) Continuously feedingan electrically conductive porous layer to a cathode materialimpregnation zone, wherein said conductive porous layer has two opposedporous surfaces and contains interconnected electron-conducting pathwaysand 70% by volume of porosity; (B) Impregnating a wet cathode activematerial mixture into said electrically conductive porous layer from atleast one of said two porous surfaces to form a cathode electrode,wherein said wet cathode active material mixture contains a cathodeactive material and an optional conductive additive mixed with a firstliquid electrolyte; (C) Introducing an anode electrode having an anodecurrent collector that has two opposed primary surfaces wherein at leastone of the two primary surfaces is deposited with a layer of an alkalimetal or an alkali metal alloy having at least 50% by weight of analkali metal element in said alloy; and (D) Stacking said anodeelectrode, a porous separator, and said cathode electrode to form saidalkali metal battery, wherein said cathode electrode has a thickness noless than 100 μm and/or said cathode active material has a material massloading no less than 15 mg/cm² for an organic or polymer material or noless than 30 mg/cm² for an inorganic and non-polymer material in saidcathode electrode.
 4. The process of claim 3, wherein step (A) and step(B) include delivering, continuously or intermittently on demand, saidwet cathode active material mixture to said at least one porous surfacethrough spraying, printing, coating, casting, conveyor film delivery,and/or roller surface delivery.
 5. A process for producing an electrodefor an alkali metal battery wherein said alkali metal is selected fromLi, Na, K, or a combination thereof; said process comprising: (A)Continuously feeding an electrically conductive porous layer to an anodeor cathode material impregnation zone, wherein said conductive porouslayer has two opposed porous surfaces and contains interconnectedelectron-conducting pathways; (B) Impregnating a wet anode or cathodeactive material mixture into said electrically conductive porous layerfrom at least one of said two porous surfaces to form an anode electrodeor cathode electrode, wherein said wet anode active material mixture orwet cathode active material mixture contains an anode or cathode activematerial and an optional conductive additive mixed with a liquidelectrolyte; and (C) Supplying at least a protective film to cover saidat least one porous surface to form said electrode.
 6. The process ofclaim 1, wherein said alkali metal battery is a lithium-ion battery andsaid anode active material is selected from the group consisting of: (a)Particles of natural graphite, artificial graphite, meso-carbonmicrobeads (MCMB), and carbon; (b) Silicon (Si), germanium (Ge), tin(Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al),nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), andcadmium (Cd); (c) Alloys or intermetallic compounds of Si, Ge, Sn, Pb,Sb, Bi, Zn, Al, or Cd with other elements, wherein said alloys orcompounds are stoichiometric or non-stoichiometric; (d) Oxides,carbides, nitrides, sulfides, phosphides, selenides, and tellurides ofSi, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti, Mn, or Cd, and theirmixtures or composites; (e) Pre-lithiated versions thereof; (f)Pre-lithiated graphene sheets; and combinations thereof.
 7. The processof claim 1, wherein said alkali metal battery is a sodium-ion batteryand said anode active material contains an alkali intercalation compoundselected from petroleum coke, carbon black, amorphous carbon, activatedcarbon, hard carbon, soft carbon, templated carbon, hollow carbonnanowires, hollow carbon sphere, titanates, NaTi₂(PO₄)₃, Na₂Ti₃O₇,Na₂C₈H₄O₄, Na₂TP, Na_(x)TiO₂ (x=0.2 to 1.0), Na₂C₈H₄O₄, carboxylatebased materials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄,C₁₀H₂Na₄O₈,C₁₄H₄O₆, C₁₄H₄Na₄O₈, or a combination thereof.
 8. The process of claim1, wherein the alkali metal battery is a sodium-ion battery and saidanode active material contains an alkali intercalation compound selectedfrom the following groups of materials: (a) Sodium- or potassium-dopedsilicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb),bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti), cobalt (Co),nickel (Ni), manganese (Mn), cadmium (Cd), and mixtures thereof; (b)Sodium- or potassium-containing alloys or intermetallic compounds of Si,Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni, Mn, Cd, and their mixtures; (c)Sodium- or potassium-containing oxides, carbides, nitrides, sulfides,phosphides, selenides, tellurides, or antimonides of Si, Ge, Sn, Pb, Sb,Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures or composites thereof;(d) Sodium or potassium salts; and (e) Graphene sheets pre-loaded withsodium or potassium.
 9. The process of claim 1, wherein said cathodeactive material contains a lithium intercalation compound or lithiumabsorbing compound selected from the group consisting of lithium cobaltoxide, doped lithium cobalt oxide, lithium nickel oxide, doped lithiumnickel oxide, lithium manganese oxide, doped lithium manganese oxide,lithium vanadium oxide, doped lithium vanadium oxide, lithiummixed-metal oxides, lithium iron phosphate, lithium vanadium phosphate,lithium manganese phosphate, lithium mixed-metal phosphates, metalsulfides, lithium polysulfide, and combinations thereof.
 10. The processof claim 3, wherein said cathode active material contains a lithiumintercalation compound or lithium absorbing compound selected from thegroup consisting of lithium cobalt oxide, doped lithium cobalt oxide,lithium nickel oxide, doped lithium nickel oxide, lithium manganeseoxide, doped lithium manganese oxide, lithium vanadium oxide, dopedlithium vanadium oxide, lithium mixed-metal oxides, lithium ironphosphate, lithium vanadium phosphate, lithium manganese phosphate,lithium mixed-metal phosphates, metal sulfides, lithium polysulfide, andcombinations thereof.
 11. The process of claim 1, wherein said cathodeactive material contains a sodium intercalation compound or a potassiumintercalation compound selected from NaFePO₄, Na_((1-x))K_(x)PO₄,KFePO₄, Na_(0.7)FePO₄, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃,Na₂FePO₄F, NaFeF₃, NaVPO₄F, KVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5),Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂,Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂,λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈,NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, KCrO₂, Na₃Ti₂(PO₄)₃,NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F,Se_(z)S_(y), y/z=0.01 to 100, Se, sodium polysulfide, sulfur,Alluaudites, or a combination thereof, wherein x is from 0.1 to 1.0. 12.The process of claim 3, wherein said cathode active material contains asodium intercalation compound or a potassium intercalation compoundselected from NaFePO₄, Na_((1-x))K_(x)PO₄, KFePO₄, Na_(0.7)FePO₄,Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃, Na₂FePO₄F, NaFeF₃,NaVPO₄F, KVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃,NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂,Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂,λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈,NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, KCrO₂, Na₃Ti₂(PO₄)₃,NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F,Se_(z)S_(y), y/z=0.01 to 100, Se, sodium polysulfide, sulfur,Alluaudites, or a combination thereof, wherein x is from 0.1 to 1.0. 13.The process of claim 1, wherein said first liquid electrolyte and/orsaid second liquid electrolyte contains a lithium salt or sodium saltdissolved in a liquid solvent and wherein said liquid solvent is water,an organic solvent, an ionic liquid, or a mixture of an organic solventand an ionic liquid.
 14. The process of claim 3, wherein said firstliquid electrolyte and/or said second liquid electrolyte contains alithium salt or sodium salt dissolved in a liquid solvent and whereinsaid liquid solvent is water, an organic solvent, an ionic liquid, or amixture of an organic solvent and an ionic liquid.
 15. The process ofclaim 1, wherein said electrically conductive porous layer has at least85% by volume of pores, said anode electrode and/or said cathodeelectrode has a thickness no less than 200 μm, said anode activematerial has a mass loading no less than 25 mg/cm² and/or occupies atleast 25% by weight or by volume of the entire battery cell, and/or thecathode active material has a mass loading no less than 20 mg/cm² for anorganic or polymer material or no less than 40 mg/cm² for an inorganicand non-polymer material in said cathode and/or occupies at least 40% byweight or by volume of the entire battery cell.
 16. The process of claim1, wherein said electrically conductive porous layer has at least 90% byvolume of pores, said anode electrode and/or said cathode electrode hasa thickness no less than 300 μm, and/or said anode active material has amass loading no less than 30 mg/cm² and/or occupies at least 30% byweight or by volume of the entire battery cell, and/or the cathodeactive material has a mass loading no less than 25 mg/cm² for an organicor polymer material or no less than 50 mg/cm² for an inorganic andnon-polymer material in said cathode and/or occupies at least 50% byweight or by volume of the entire battery cell.
 17. The process of claim1, wherein said electrically conductive porous layer has at least 95% byvolume of pores, said anode electrode and/or said cathode electrode hasa thickness no less than 400 μm, and/or said anode active material has amass loading no less than 35 mg/cm² and/or occupies at least 35% byweight or by volume of the entire battery cell, and/or the cathodeactive material has a mass loading no less than 30 mg/cm² for an organicor polymer material or no less than 55 mg/cm² for an inorganic andnon-polymer material in said cathode and/or occupies at least 55% byweight or by volume of the entire battery cell.
 18. The process of claim1, wherein said electrically conductive porous layer is selected frommetal foam, metal web or screen, perforated metal sheet-based structure,metal fiber mat, metal nanowire mat, conductive polymer nano-fiber mat,conductive polymer foam, conductive polymer-coated fiber foam, carbonfoam, graphite foam, carbon aerogel, carbon xerox gel, graphene foam,graphene oxide foam, reduced graphene oxide foam, carbon fiber foam,graphite fiber foam, exfoliated graphite foam, or a combination thereof.19. The process of claim 6, wherein said pre-lithiated graphene sheetsare selected from pre-lithiated versions of pristine graphene, grapheneoxide, reduced graphene oxide, graphene fluoride, graphene chloride,graphene bromide, graphene iodide, hydrogenated graphene, nitrogenatedgraphene, boron-doped graphene, nitrogen-doped graphene, chemicallyfunctionalized graphene, a physically or chemically activated or etchedversion thereof, or a combination thereof.
 20. The process of claim 1,wherein said cathode active material comprises an alkali metalintercalation compound or alkali metal-absorbing compound selected froman inorganic material, an organic or polymeric material, a metaloxide/phosphate/sulfide, or a combination thereof.
 21. The process ofclaim 20, wherein said metal oxide/phosphate/sulfide is selected from alithium cobalt oxide, lithium nickel oxide, lithium manganese oxide,lithium vanadium oxide, lithium-mixed metal oxide, lithium ironphosphate, lithium manganese phosphate, lithium vanadium phosphate,lithium mixed metal phosphate, transition metal sulfide, or acombination thereof.
 22. The process of claim 20, wherein said inorganicmaterial is selected from sulfur, sulfur compound, lithium polysulfide,transition metal dichalcogenide, a transition metal trichalcogenide, ora combination thereof.
 23. The process of claim 20, wherein saidinorganic material is selected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂,an iron oxide, a vanadium oxide , or a combination thereof.
 24. Theprocess of claim 20, wherein said metal oxide/phosphate/sulfide containsa vanadium oxide selected from the group consisting of VO₂, Li_(x)VO₂,V₂O₅, Li_(x)V₂O₅, V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉, Li_(x)V₄O₉, V₆O₁₃,Li_(x)V₆O₁₃, their doped versions, their derivatives, and combinationsthereof, wherein 0.1<x<5.
 25. The process of claim 20, wherein saidmetal oxide/phosphate/sulfide is selected from a layered compound LiMO₂,spinel compound LiM₂O₄, olivine compound LiMPO₄, silicate compoundLi₂MSiO₄, Tavorite compound LiMPO₄F, borate compound LiMBO₃, or acombination thereof, wherein M is a transition metal or a mixture ofmultiple transition metals.
 26. The process of claim 20, wherein saidinorganic material is selected from: (a) bismuth selenide or bismuthtelluride, (b) transition metal dichalcogenide or trichalcogenide, (c)sulfide, selenide, or telluride of niobium, zirconium, molybdenum,hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel,or a transition metal; (d) boron nitride, or (e) a combination thereof.27. The process of claim 20, wherein said organic material or polymericmaterial is selected from Poly(anthraquinonyl sulfide) (PAQS), a lithiumoxocarbon, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquino-dimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.
 28. The process of claim 27,wherein said thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).
 29. The process of claim 20,wherein said organic material contains a phthalocyanine compoundselected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.
 30. The process of claim3, wherein said cathode active material contains an alkali metalintercalation compound or alkali metal-absorbing compound selected froma metal carbide, metal nitride, metal boride, metal dichalcogenide, or acombination thereof.
 31. The process of claim 1, wherein said cathodeactive material contains an alkali metal intercalation compound oralkali metal-absorbing compound selected from an oxide, dichalcogenide,trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium,molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium,cobalt, manganese, iron, or nickel in a nanowire, nano-disc,nano-ribbon, or nano platelet form.
 32. The process of claim 3, whereinsaid cathode active material contains nano discs, nano platelets,nano-coating, or nano sheets of an inorganic material selected from: (a)bismuth selenide or bismuth telluride, (b) transition metaldichalcogenide or trichalcogenide, (c) sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, cobalt, manganese, iron, nickel, or a transition metal; (d)boron nitride, or (e) a combination thereof; wherein said discs,platelets, or sheets have a thickness less than 100 nm.